The prospect of a general election on May 5 now looks almost certain after it was announced on Thursday that Prince Charles and Camilla Parker-Bowles are to be married about a month earlier.
The decision to hold the royal wedding on April 8 was taken in close consultation with the prime minister.
The wedding has been carefully timed to ensure it does not occur in the middle of the four-week general election campaign, which will formally begin three days later on April 11.
Mrs Parker Bowles will take the title HRH Duchess of Cornwall after a civil ceremony at Windsor Castle. When the Prince of Wales, 56, becomes king, 57-year-old Mrs Parker Bowles will not be known as Queen Camilla but as the Princess Consort, Clarence House said.
Thursday's announcement means the timetable for the final few weeks of this parliament is now becoming clearer. Gordon Brown's Budget will be delivered on, or around, March 16. Tony Blair is likely to ask the Queen to dissolve parliament and call an election on, or around, April 6.
The expectation of an election on May 5 was heightened on Thursday when a senior Russian lawmaker said Mr Blair would not visit Moscow for the 50th anniversary of VE day on May 9.
"Tony Blair said there will be elections in his country on May 5, and that is understandable," said Konstantin Kosachyov, chairman of the State Duma foreign affairs committee.
Clarence House had been planning to announce the royal wedding at the end of next week but a report in the Evening Standard forced the news to be brought forward.
The announcement risks undermining coverage of Labour's spring conference this weekend, at which the government is planning to unveil key details of its election campaign.