Ministers were warned in July 2002 that Britain was committed to taking part in an American-led invasion of Iraq and they had no choice but to find a way of making it legal.
The warning, in a leaked Cabinet Office briefing paper, said Tony Blair had already agreed to back military action to get rid of Saddam Hussein at a summit at the Texas ranch of President George W Bush three months earlier.
The briefing paper, for participants at a meeting of Blair’s inner circle on July 23, 2002, said that since regime change was illegal it was “necessary to create the conditions” which would make it legal.
This was required because, even if ministers decided Britain should not take part in an invasion, the American military would be using British bases. This would automatically make Britain complicit in any illegal US action.
“US plans assume, as a minimum, the use of British bases in Cyprus and Diego Garcia,” the briefing paper warned. This meant that issues of legality “would arise virtually whatever option ministers choose with regard to UK participation”.
The paper was circulated to those present at the meeting, among whom were Blair, Geoff Hoon, then defence secretary, Jack Straw, the foreign secretary, and Sir Richard Dearlove, then chief of MI6. The full minutes of the meeting were published last month in The Sunday Times.
The document said the only way the allies could justify military action was to place Saddam Hussein in a position where he ignored or rejected a United Nations ultimatum ordering him to co-operate with the weapons inspectors. But it warned this would be difficult.
“It is just possible that an ultimatum could be cast in terms which Saddam would reject,” the document says. But if he accepted it and did not attack the allies, they would be “most unlikely” to obtain the legal justification they needed.