Peeking out from behind swathes of mist and murk great paintings emerge at Tate Britain’s ‘Impressionists in London’ exhibition, but you have to wade through some dreadful muck to get there.

I know you won’t take a blind bit of notice of what I say, but if you plan to visit this exhibition,  do wear trainers. You’ll want to go at quite a lick.

Room 1: With the Prussians beating the bejesus out of Paris in1871, French artists, including Camille Pissarro, Charles-Francois Daubigny and a young Claude Monet decamped to London in many cases to paint pictures of Sydenham. I mean I have nothing against Sydenham, but with your home city in flames, doesn’t London have a bit more to offer? Nothing to see here, keep moving.

Room 2: By now you really want to be building up a good head of steam, perhaps whip out a skateboard and marvel, as you glide by, at the awfulness of the Quality disporting themselves in paintings by James Tissot of well, the Quality disporting themselves. These paintings are why photography was invented so nobody has to do this stuff anymore.

I’m also not sure what any of this has to do with impressionism, looks more like expressionism to me.

On! On! past Alphonse Legros doing his worst and as quick as you like through the room dedicated to the ‘celebrated’ sculptor Jean-Baptiste Carpeaux. I don’t know about you, but I only notice sculpture when I’m backing up to get a good look at a painting and then bash into it.

By the time you reach Room 5 you’ll have reached optimum velocity, but hold up is that a painting worth looking at? Yes, it is and it’s Monet’s ‘Leicester Square at night’, great splodges of greasy reds and blues. Perhaps not Monet in mid-season form, but certainly worth a glance.

It’s funny I’m sure I used to like Pissarro, I remember enjoying a couple of his paintings at the Ashmoleum in Oxford years ago, but now they look incredibly trite, almost chocolate-box, paint by numbers kitsch.

By the time you enter Room 6 you may be losing the will to live, but help is at hand in the form of three paintings or nocturnes by the American artist James McNeill Whistler. They are simple washes of grey blue, with lonely stick figures haunting the canvas, but taken together are magnificent. They are owned by the Tate but don’t often get a run out. Oscar Wilde commenting on his friend Whistler’s work in typical Oscar style said: ‘There may have been fogs for centuries in London. I dare say there were. But no one saw them, and so we know nothing about them. They did not exist until art had invented them.’

This exhibition really ought to carry a weather warning as the dense fog leaks from Room 6 and blankets the next room. It’s a regular pea-souper in Room 7, which holds Monet’s celebrated pictures of the House of Commons and Big Ben. You can hardly see the nose in front of your face.

Monet, in his sixties, came to London for three consecutive winters saying he wished ‘to sum up…impressions and sensations of the past’ and there is a melancholy, retrospective quality to the pictures. Staying at The Savoy, one room for sleeping and one for painting, he would venture out into the gloom at about 4 o’clock to capture the sun going down. Surely, these must be some of the greatest pictures of London. Fog swathes Big Ben and the Palace of Westminster as the fading sun hits the Thames; they make London look as beautiful as Venice.

Here’s the question: when these pictures were complete and put on sale how many were sold in London? Not one, nada, zip. We don’t want that weird, modern, foreign rubbish round here thank you very much.

The ‘Impressionists in London’ exhibition is 60% dreadful, 20% mildly interesting and a further 20% utterly magnificent. It costs £19.70 to get in, you do the maths. For me the three Whistler paintings alone are worth the price of admission.

Open until 7th May 2018

On my way out I spotted a fantastic exhibition by Bernard Cohen, an artist new to me. It’s free and definitely worth a look. Here’s one now.