The Christmas tree lights in Trafalgar Square are being powered by a hydrogen fuel cell following a special ceremony last night.

The move comes as part of the Greater London Assembly's commitment to supporting green energy.

The project to replace traditional mains electricity with a hydrogen fuel cell was sponsored by the energy company BOC and the platinum refiner Johnson Matthey, both members of the London Hydrogen Partnership.

Ken Livingstone, the mayor of London, is working with the London Hydrogen Partnership to demonstrate the viability of hydrogen and fuel cells in the capital.

"This is a significant initial step towards establishing a hydrogen fuel cell economy in London," said deputy mayor, Nicky Gavron.

"This is the first time in Europe a fuel cell has been used in this way and will show that this is a viable alternative to the noisy and dirty petrol and diesel generators currently used.

The fuel cell was invented in London 160 years ago. As well as Christmas tree lights, fuel cells could one day power London's buses.