Becoming Picasso, Courtauld Gallery, London

The Courtauld Gallery, which has brought us a succession of tightl focused small exhibitions in recent years, has come up with another real stunner. Becoming Picasso is the story of the Spanish painter’s arrival – brash, determined and hungry for the bohemian life – in the French capital in 1901.

Working feverishly by day and night, he knocked up as many as two or three paintings a day in his Montparnasse studio for an opening show held by the notable French dealer Ambroise Vollard. It was both a declaration of arrival, as he took the style and images of Van Gogh, Lautrec, Degas and Gauguin and reworked them at will, and an instant success with the critics. It was also the turning point for the artist, who, instead of building on his new reputation for colour and frenzy, then developed a more sombre palette and subject matter in the paintings of his Blue Period the same year.

You can see both why he so wowed the critics and how he then moved in another, much less commercially successful direction (he was virtually destitute by the end of the year) in this compulsive show. It has obtained 10 of the 60 paintings in the original Vollard exhibition. All have the sense of hurried works, but all equally bear a confidence that is quite staggering in a man so young. A picture of the Dwarf Dancer (La Nana) combines the colour of Lautrec with a dwarf figure from Velázquez – but then has a face of ferocious defiance that is entirely Picasso’s.

The maturing of an individual style comes across remarkably as you move into the main room of this show. Along one wall the Courtauld has assembled four early masterpieces rarely lent outside their homes in Russia and the US. Child with a Dove, once owned by Samuel Courtauld, the Seated Harlequin, Harlequin and Companion and The Absinthe Drinker introduced the themes which he was to reiterate all his life – but they also introduced a mood that was more introspective and melancholy than anything he’d done before.

The gallery puts the change partly down to the suicide of his closest friend, the poet Carles Casagemas, here represented by an imagined blue picture of him in his coffin, which Picasso kept secreted away in his studio until the 1960s.

How sincere Picasso ever was in his egocentricity is always difficult to fathom. The death of his friend and his visits to a women’s prison may have moved him to melancholy, but he was also probably aware that painting dizzying pictures of Gay Paris was a dead end. He needed to become more serious and that he did with a vengeance.

To 26 May (020 7848 2526)