A painting by Leonardo da Vinci was transformed as a result of restoration at the National Gallery – and is now thought to be the result of the master artist working alone.

Virgin of the Rocks, which was commissioned in 1483, looks radically different as a result of 18 months of painstaking cleaning.

The mountains are now a vivid blue, the flowers and leaves full of detail, the Virgin has lost her greenish pallor, her hand now appears to reach out and the whole painting has a sense of space that was previously absent.

Virgin of the Rocks was attributed to Leonardo da Vinci’s workshop in Milan, but it is now thought it is possible it was produced by the master artist working alone.

The National Gallery’s Director of Conservation Larry Keith, who restored the painting, said: “The cleaning process has brought out the modelling of light and dark in the painting, the three dimensionality. That’s the real revelation. That was very important to Leonardo. You can see the dark colours much better now.” The area under the Virgin’s sleeve now reads as a hollow, the landscape now goes backwards and the shelf of the rocks in the foreground now appears to undulate.

Restorers focused on removing a cracked, yellowed and waxy surface of varnish from the painting, which was applied in 1948, and which obscured the subtlety of shading and sense of space.

The process confirmed suspicions that the Virgin of the Rocks was unfinished – as a perfectionist da Vinci was famous for being indecisive and very few of his paintings were completed.

While the heads of the principal figures were finished, the hand of the angel is barely sketched.

In the past, experts explained the different levels of finish by arguing that the Italian artist was helped by assistants but the National Gallery said it now seems possible he may have painted all the picture himself.