Banker gives Tate record £5 million for 2012 extension

The donation will enable the Tate to press ahead with plans for the £215 million development, which it hopes to have open in time for the Olympics in 2012.

Mr Studzinski said he was delighted with the vision for transforming the landmark building in Bankside.

"Tate Modern has been an extraordinary success under Nicholas Serota's vision and leadership and has a great track record," he said. "I believe in backing winners."

The London Development Agency has already donated £7 million to kick-start the annexe, designed to be in the form of a spiralling, stepped pyramid, or ziggurat.

Announcing the gift, which is £2million more than the previous largest donation to the original Tate Modern, Sir Nicholas said it provided leverage to raise money from other potential donors.

"John has been an important figure for the Tate in helping us raise money from other people. It gives him credibility when he's asking other people and it sets the bar at quite a high level," he said.

The Tate also announced today it is to carry out a major consultation on the future of the gallery.

It is to discuss collaborations with other institutions on the South Bank, such as the British Film Institute, with which it has presented film programmes, and the Design Museum.

The first stage of the consultation takes place next Tuesday when 150 young people have been invited to sleep in the Turbine Hall in tents. They will be asked to consider options for the development of the building.

Sir Nicholas said: "I'm genuinely intrigued by what people will say. If I had to forecast, one of the things that will come out is that people will want to participate much more than simply being passive learners. The question is how we encourage that participation."

Ideas already in motion include a mobile Tate to travel across the country and plans for projects involving Premier League football.