It was Sir Menzies Campbell who made the first move in the political flirtation that has rebounded so damagingly on him.

Two weeks ago, as Westminster’s attention was fixed on the G8 summit in Germany, Sir Menzies sent a letter to Gordon Brown proposing two new cross-party policy commissions.

All three main parties want changes to the constitution and faster progress in curbing climate change, wrote the Lib Dem leader, why not work together on these issues?

The incoming prime minister was intrigued. He asked Alistair Darling to make contact with one of Sir Menzies’s closest allies, Lord Kirkwood of Kirkhope, to discuss the proposals at greater length.

It was not, therefore, a complete surprise when Sir Menzies was told early on Monday afternoon that Mr Brown wanted to see him as soon as possible in his Commons office. It was from the moment that he left his own suite of rooms and travelled down a flight of stairs towards the Chancellor’s office that the trouble began.

In a 30-minute, one-to-one meeting, Mr Brown said that he was willing to go much farther than Sir Menzies had suggested and wanted to bring Lib Dems into his government. In particular, he said, he wanted to offer Lord Ashdown of Norton-sub-Hamdon a post.

Later, justifying his failure to turn on his heels and leave as soon as the idea was floated, Sir Menzies said that he had been scarred by the fallout from David Cameron’s surprise proposal to field a joint London mayoral candidate. He did not want to be criticised again for failing to consult his party and asked for 24 hours to consider the proposal.

It now seems that Mr Brown was not content to let the party leader take his decision without letting Lord Ashdown know what was being offered him and he left a message asking the peer to see him urgently.

Sir Menzies was nonplussed to receive a call from Lord Ashdown asking why the next prime minister wanted to see him. He had told only Lord Kirkwood and close ally Ed Davey, MP, about the offer — but now Lord Ashdown knew.

Lord Ashdown insisted yesterday that he had accepted his leader’s decision that he should not serve in a Brown government at once. A close aide to Sir Menzies said last night: “Paddy was clear that this wouldn’t fly.”

It remains, curious, however, why Sir Menzies still did not pick up the telephone and tell the Chancellor that there could be no question of any Lib Dem ministers in his administration. His office said that he intended to do so at a meeting scheduled for Tuesday but that that appointment was cancelled at Mr Brown’s request and rebooked for the Wednesday.

Before the two men could meet face-to-face, however, news of their discussions leaked. Lord Kirkwood awkwardly failed to deny that talks were under way when contacted by The Guardian. The subsequent coverage — incorrectly suggesting that MPs might be invited into the Brown Government — enraged Lib Dem MPs who feared their leader was about to make a terrible strategic error.

A spokesman for Sir Menzies did not deny that his leadership was questioned: “Yes it was a leadership issue yesterday \ morning when people did not know what was happening.” Asked whether Sir Menzies regretted not ruling out Liberal Democrats entering a Brown government the moment he was asked, the spokesman said: “Absolutely.”

Worse was to come for Sir Menzies, however, as Lord Ashdown decided to accept an invitation to see Mr Brown face to face in his Treasury office even as the internal row prompted by the story was raging. At the meeting the Chancellor made clear what was on the table: a seat in the Cabinet as Northern Ireland secretary. The peer, brought up in the Province, may have been tempted but made clear that his leader would not allow it and he was not going to defy him.

It is not clear whether Sir Menzies knew about the Treasury meeting when he addressed Lib Dem MPs in a Commons meeting later that day. His assurance that he had never had any intention of going into government with Mr Brown calmed his troops but he still faced awkward questions about how the story had been allowed to leak.

The Chancellor’s allies say they suspect that a Liberal Democrat MP may have leaked the details in order to kill the talks, or it was the result of loose talk from one of those in the know. They categorically deny sucking the Lib Dems into a trap. Although some left-wing Labour MPs are unhappy and the Tories claim the affair amounts to a “giant snub” to Mr Brown, Mr Brown is probably not displeased at the outcome of the affair. He can say that he has demonstrated an openness to new ideas and new personnel. The consequences of the affair for Sir Menzies are much more dangerous. Twice now he has been caught out by the machinations of other party leaders. A third embrace could be deadly.

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