When the gallery is open to the public uniformed Gallery Assistants help provide a safe and welcoming environment for visitors to enjoy the paintings. Trained to identify and deal with potential risks to the Collection they fulfil an important dual role in visitor service and security.

Maybe the Getty, since they finally got their hands on Turner's Modern Rome last year?  And they have been spending vast amounts of cash on acquisitions of late.

Modern Rome was their second painting by Turner of course, the other being the ex-Holloway College Van Tromp; and they have two watercolours.  But nothing by Constable as yet so this is their only opportunity to get a really important one.  I doubt somehow that his last great six-footer, still in private hands, would be allowed out of the country.

Fortunately, the portrait of Henry VIII is owned by the Spanish State, and like all works of art from national museums,is inalienable, in contrast to Constable's 'Lock' which is owned by the Baroness and only was on loan to the Thyssen museum with the rest of the Carmen Thyssen collection, but the collection of her husband, With Van Eyck, Duccio, Caravaggio, Carpaccio, Weyden, Bacon, etc is owned by the Spanish.

The auction house said it was to sell the only one of Constable's Stour series - which includes The Hay Wain in the National Gallery - that remains in private hands.

Jussi Pylkkänen, president of Christie's Europe, said The Lock was "one of John Constable's greatest paintings and an outstanding masterpiece of British art". He added: "This superb landscape, coming from the same series as The Hay Wain, represents British landscape painting at its very best and is sure to attract bidding from museums and collectors from all over the world."

UK museums are unlikely to have deep enough pockets for a work that, when it was bought at auction in 1990, set a record for a British work of art. It was bought for £10.8m and held the record until 2006 when a view of Venice by Turner, Constable's rival, sold for £20.5m at Christie's in New York. Another Turner sold for £29m at Sotheby's in London in 2010.

The present composition would appear to be the right hand extremity of Reni's original Bacchus and Ariadne, showing two faun followers of Bacchus with Silenus beyond, on his donkey, supported by two putti.  Upon firsthand inspection of the work both Keith Christiansen and David Stone recognized the hand of Guido Reni in the faces of the fauns and in the hands holding the tambourine though suggested, as with the majority of Guido's large scale compositions, the likely involvement of his studio in the execution of certain passages.  Camillo Manzitti, meanwhile is in favor of a full attribution to Guido Reni, believing this work to indeed be a fragment of the original.  He furthermore suggested that the addition to the right edge of the painting was executed in order to centralize the figures within the composition andto avoid any concealment of Silenus by an eventual framing of the work.

Although there are indeed variances in detail between Bolognini's engraving and the present composition, these would appear incidental.  The drapery over the hip of the right hand figure may have been added later and so too the still life of flask and glass of wine, perhaps subsequent to the painting's division in order to bestow the fragment with the more cohesive and traditional composition of a Bacchanal.  Yet the presence of a tambourine, under the feet of the larger faun and still visible to the naked eye below the paint surface, provides a compelling argument in favor ofthe fragment's origin.  This corresponds with the engraving closely and may have been covered over at the time the other changes were made. This Two Fauns in a Bacchic Dance is not the first fragment from the composition tosurvive; in 2002, Denis Mahon and Andrea Emiliani discovered a fragment portraying the beautiful and vulnerable figure of Ariadne, now in the Pinacoteca Nazionale di Bologna.The addition to the left hand edge of the Ariadnecanvas shows that, far from being obliterated, the canvas had been carefully cut to preserve the figures, presumablyto facilitate their sale as individual fragments.  It too is painted on a heavy weave canvas that appears to correspond to that used in the present picture. 

My own first encounter with these little tyrants was at Saltram near Plymouth, which I was visiting as part of my research for a Reynolds exhibition. Reynolds was close to the family that remodelled the house in the late 1760s and early 1770s & we were borrowing their two best Reynoldses.

There is an old guidebook to the pictures at Saltram by Nigel Neatby, still useful now but of course the hang has changed over time, so I wanted to make a note of the current location of everything, which I did by scrawling on my paper a very rough elevation of each wall, with a numbered square for the location of each picture. In every room I introduced myself to the steward and explained who I was and what I was doing. In one room, the steward asked me if I had permission, to which I replied that surely I didn't need permission, I was just taking notes of the pictures. This was my mistake. When I was in the Saloon, a very short and angry man stormed up to me and demanded to know what on earth I was doing, that sketching was absolutely forbidden, that I could be a burglar etc. Even the steward in the Saloon tried to intercede on my behalf. The upshot was that I was permitted to continue to make notes, but I could no longer arrange my information within squares, as that would constitute drawing. What made me most cross is that most of the pictures at Saltram aren't even worth stealing.

Come to think of it, when I was at Powis Castle the other month, I asked a room steward if it would be ok for me to check his folder of information as I was interested in one of the pictures. He totally forbade it, and then got very cross and flustered when I asked him to look up the attribution (a Marlow landscape), all the while telling me about the two Gainsborough Duponts either side of it, about which he was clearly more used to talking.

The point is really that life in these National Trust houses seems incredibly scripted. They are used to people filing through and expressing delight at their tired old stories about how the 5th Countess snogged George Bernard Shaw under the sofa etc etc, but too often they cannot cope when a visitor doesn't conform.

I agree with most of your blog posts, but I have the opposite view of NG guards.  Several times I've seen people poking or stroking paintings at the NG, with guards doing nothing.  I remonstrated with one who refused to intervene, and he said that people only complain if he says anything.  He said that people have even kissed the Infant Christ in renaissance paintings.  I raised this directly with the Head of Security, who was immensely helpful.  He met with me, explained their policies, showed me the manuals used by the guard staff and went around the galleries with me to meet some of the guards.  Incidentally the Head of Security is knowledgeable and passionate about art himself (he keeps part of his personal collection of maritime paintings in his office, where they cost more to insure than in his home!).

Notwithstanding a few incidents, I've found NG guards to be generally alert, helpful and polite - certainly far more than in American and Italian museums, which I find the be worst.

I understand your annoyance, and I've been told off too.  But when it's a balance between protecting the art and protecting patrons' feelings, I know which way I'd like them to err.

Female genitalia have long been a source of fascination, recently of celebration but generally of confusion. Today it seems that creating images of the vagina is the sole preserve of pornographers, erotic artists and feminists. Step in British artist Jamie McCartney who has grasped the nettle to create a monumental wall sculpture all about this most intimate of places. For 400 women their privates have gone public... [...]

It’s not vulgar, it’s vulva! This isn’t just sensation, it is art with a social conscience and McCartney wants people to stop, look and listen. This is about grabbing the attention, using humour and spectacle, and then educating people about what normal women really look like. Described as “the Vagina Monologues of sculpture” this piece is intended to change the lives of women, forever. [...]

The Great Wall of Vagina makes for fascinating and revealing viewing which is a far cry from pornography. It is not erotic art. It is not about titillation. McCartney has pulled off an amazing trick - to deliberately make the sexual nonsexual and take you much deeper.

I was sorry to hear about the Courtauld librarian - very annoying for you, and very out of date of them. 

It reminds me of the old days when you had to pretend you were visiting the Heinz Archive simply for fun.

I exchanged letters with a venerable (and ultimately very nice) eminence a while ago who noted that the Trade always want to barter academics' lifetime expertise into £££s on a price tag.

Very true, I said, but the Trade is the plough constantly churning up treasure for academics to publish and make their reputations on.

Presumably you sent some people round at closing time to 'explain things', the librarian in an armlock while the rest of the boys do a bit of mis-shelving.

I wouldn't want words written in indignation on your behalf to be taken askance by your academic readers. May I pay tribute to them? Everyone in the Trade is indebted to academic art historians for sharing their time, their opinions and their imprimatur so generously. Their work is a bedrock of centuries stretching back to Vasari, and anything we achieve is built on that.

It appears that the National are going to be given two of the paintings shown in their recent exhibition of the Lunde collection [The Lower Falls of the Labrofoss by Johan Christian Dahl, above, and At Handeck by Alexandre Calme].

Two things are interesting about this.

The Dahl and Calame will actually be given to the Gallery's not-for-prodit arm based in New York - the American Friends of the National Gallery London - for tax reasons I imagine.  As you know gifts of works of art to charities in the US attract tax relief but this option has only been introduced in the UK from 1st April this year.  The government are now proposing to limit any charitable gift to £50,000.  

Aside from the fact that the AFNGL holds the donation from Sir Paul Getty and is used to filter other US gifts of money, again for tax reasons, this mechanism has been used before to donate at least one other work of art.  The Sara Lee Foundation gave them this Degas in 1998.

The other interesting element is the acquisition of 19th C Northern European landscape paintings itself.  Unlike the Met, the National has not collected extensively in this field aside from the two Danish scenes, the Balke given to them last year, and the surprising - and brilliantly imaginative - purchase of the Gallen-Kallela in 1999.

As far as I am aware, there are only a couple of Dahls (Johan Christian not Michael!) in any UK collection - at the Barber and the Fitzwilliam - and they are more typical of the sort of Dahl other institutions have been buying.

Calame is better known, and was collected in the UK in the 19th C - the National already has one example given in 1900 though, oddly, in the item on the exhibition in the June 2011 podcast one member of gallery staff seems not to be aware of the fact.

Of course, if the Gallery had wanted to have a better display of this sort of painting, it need only have borrowed from the V&A, which holds two paintings by Calame, as well as works by Steffan, Diday, Schleich, Baade and lots of others of that ilk.

Not sure this is quite 'on topic' for your blog, but I noticed in Country Life yesterday that Apethorpe Hall in Northamptonshire has been put up for sale by English Heritage, through Savills, for £2.5m.

It's an amazing building but years of neglect left it on the verge of ruin, such that English Heritage compulsorily purchased it in 2004, under the 1990 Planning Act, only the second time these powers had been used. It cost £3.6m, plus a further £4m restoring the basic fabric. So £7.6m in all.

If the house goes for the asking price - and it will only be sold to someone willing to commit to further very expensive work, who's happy to let the public in for 28 days a year, can deal with some annoying trees that are owned separately, and doesn't mind that it comes with next to no land - the taxpayer will have lost over £5m.

One of your readers wrote;

".....and doesn't mind that it comes with next to no land"

Yes, only 45 acres according to the details - barely worth employing a gardener then.