Colourful batik sails are set to the darker history of colonialism

When Yinka Shonibare told the crowds at Trafalgar Square today that he had been waiting for this moment for a long time, I sense that he wasn't just talking about the three years that have passed since he first presented his idea for Nelson's Ship in a Bottle.

Trafalgar Square is the ideal platform for the ideas that Shonibare has been exploring since the early Nineties, and this feels like the work he has been leading up to for all those years.The square is our monument to the British Empire, with its statues to imperial heroes such as Henry Havelock, Charles James Napier and, of course, Horatio Nelson - and ideas of empire and colonialism have dominated Shonibare's work. His signature material, the colourful batik which forms the Victory's sails, was chosen precisely for its contradictory history. We associate it with African dress, but it actually originated in Indonesia and was industrialised in Holland, before being shipped to Africa.

The fabric Shonibare uses is fabricated in Manchester and bought in Brixton market.

Like all Shonibare's best work, it is playful and exuberant, but it's not entirely celebratory - in equipping the Victory with sails made of this ambiguous material, he asks us to reflect on the darker history of colonialism, its exploitation and its cruelties.

I don't doubt Shonibare's sincerity in using the Victory to reflect London's present diversity and its status as a great cosmopolitan city, but its also has a sting in its tail, and that's what makes it one of the best fourth plinth artworks to date.