That programme on Five last night was remarkable. Whereas the BBC1 programme last week went out to Madrid and filmed in the city, at the royal hunting lodge, at the riding school, at the palace, at the Prado and possibly even in Rome (I lost track) with huge amounts of Ken Morse rostrum work, this one had a much smaller budget and stayed entirely in the National Gallery.

It was just a tour round the four rooms of the current exhibition, with Tim Marlow standing in front of paintings and talking about them but I cannot remember the last time 45 minutes went by so quickly. One drawback was that works not in the exhibition were only mentioned in passing, and a couple of the best Velzquez works are not in the exhibition, but even so it really does look like the place to go – even if only to see that amazing portrait of Pope Innocent, or rather the copy of it.

That in itself is a bit of a mystery. The original painting is in Rome and will not move from there, but the copy in London was either painted afterwards by Velazquez’s staff with some input by him, or was painted by Velazquez himself before the other one as a very elaborate preliminary sketch done in oils. The experts are divided on this, but Tim Marlow makes a good case for the one in London actually being the original. The papal robes are vague and undefined compared to the Rome painting but the face is the same powerful, slightly scary image.

I had not seen it before last week, but I think it could well be my favourite portrait now. Mind you , I have yet to see the hilarious ‘cabbage patch Queen’ portrait at the Tate Modern so perhaps I should reserve judgement until I have…