Mr Patten refused to stand until he was convinced it was a real job, but a friend said: "We are hoping he will now decide to stand. There are real powers for the new mayor." Mr Patten is seen by some Tories as the best hope to stop Lord Archer, the author, and so far the most enthusiastic campaigner for the post.
Frank Dobson, the Secretary of State for Health, was emerging as Tony Blair's preferred choice to run against Ken Livingstone, the former Greater London Council leader, and Labour MP, who announced yesterday he would be standing.
Mr Dobson has made it clear he wants to continue with his cabinet role, but that could change next year if he was invited to stand. He is viewed by the Labour leadership as the strongest candidate to beat Mr Livingstone, a member of the party's national executive with a following from his days as the charismatic boss of the GLC.
Glenda Jackson, transport minister for London, will also declare her hand after the 7 May referendum, which is expected to be overwhelmingly in favour of having an elected mayor. The Tories did a U-turn, and confirmed yesterday they would be campaigning with Labour and the Liberal Democrats for a "yes" vote, putting the result beyond doubt.
The Deputy Prime Minister, John Prescott, gave the clearest signal so far that the elections for mayor and assembly will be brought forward to autumn 1999, to put both in place in time for the millennium, and well before the next election.
Mr Prescott said the new mayor would be "a powerful figure" with an electorate of more than five million voters.
The mayor will be elected by supplementary vote, allowing voters to mark their first and second choices of candidate, while the 25-member assembly will be elected by the additional-member system, with 14 directly elected by the first-past-the-post vote and 11 drawn from London-wide lists to reflect the position of the parties. It is likely that Labour will ensure places for women and ethnic minorities by this system.
The White Paper unveiled by Mr Prescott will put the mayor and the directly elected assembly in charge of a pounds 3.3bn budget with powers over police, fire, and transport services - buses, roads, river services and a say in the future of London Underground. There will be a new 23-strong Metropolitan Police Authority, with 11 drawn from the assembly. The Home Secretary will appoint 11 members and one will be drawn from the district councils outside London.
The potentially most controversial powers are over the boroughs, and Sir Norman Fowler, Tory environment spokesman, protested that the importance of the boroughs was being reduced. The mayor will have strategic power of planning, with the right to reject planning permission for developments that do not fit in with his plans; disputes will be decided by the Secretary of State for the Environment. The mayor will set the Budget, which will have to be approved in a vote each year by the assembly.
The Government has yet to decide where the greater London authority (GLA) will be based, but possible locations for its offices include County Hall, the former GLC building; Canary Wharf and Admiralty Arch, which was used for the homeless at Christmas.
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