It was Sir Menzies Campbell’s closest friends, not plotters or assassins, who told him the brutal truth — that the game was almost up and it was time to think of standing down.

Far from falling victim to a coup at the hands of his MPs, the Liberal Democrat leader left Commons colleagues in the dark as he took soundings from a trusted group of long-time allies over his fate. The task was entrusted to Lord Kirkwood of Kirkhope, Sir Menzies’s friend and counsellor, who made discreet telephone calls over the weekend to “core supporters” to ask if he should carry on. Among them was Lord Ashdown of Norton-sub-Hamdon, who said that his situation was tough but that if he did quit it should be on his own terms.

It was a speech in a school hall in East Anglia at the weekend that proved to be the turning point. After addressing a dinner for Lib Dems in Rochdale on Friday night, Sir Menzies travelled to a technical college in Mildenhall, Suffolk, on Saturday to address a regional party conference.

He was fluent and passionate and gave one of his best performances as leader as he told the assembled Lib Dems that he answered to them, not to the media, and still had “the energy, the ideas and the determination” to carry on as leader. “He did an absolute textbook weekend of campaigning,” a close ally said. “He got a great reception, then he came back to a sea of attacks and personal abuse. It was at that point he suddenly realised it didn’t matter how good he was, what he did. He was still going to fail to get the message across.”

A rash of bruising press stories awaited Sir Menzies as he returned to Edinburgh, sparked by comments from Simon Hughes that the party leader “has to do better”. With no general election due until the spring of 2009, he knew that he faced 18 months of such criticism, or longer, unless he could turn the tide.

Sir Menzies had already been considering his fate. On Friday he asked those around him what they thought. Mark Webster, his chief press spokesman, told him that he could survive, at least until the spring; it was far from the endorsement that he needed.

In the face of the renewed media onslaught, Sir Menzies asked Lord Kirkwood to conduct a ring-round of core supporters, people whose discretion could be trusted and whose judgment he prized. On Monday morning, after Sir Menzies flew to London, Lord Kirkwood reported his findings. He had earlier told a confidant: “I cannot let my friend die by a thousand cuts.”

They met alone in the leader’s Commons office where, according to friends, they examined newspaper clippings together. Lord Kirkwood’s assessment was not quite clear-cut. He advised his friend that he had two options: be brutal and grasp the agenda to fight on, or go now and protect his legacy by handing on to someone else.

The party’s chief whips in the Commons and Lords, Paul Burstow and Lord Shutt of Greetland, were asked to feed into the process and take soundings among MPs and peers but Sir Menzies’s mind was rapidly made up. “He made his own decision,” another friend said. “He knew what those close to him thought. Ultimately it was through a lawyer’s eyes that he looked at the evidence and decided.”

In fact most MPs, even those who worked closely with him, were taken by surprise when he resigned. Having decided his fate, Sir Menzies resolved to return to Edinburgh rather than face a potentially undignified press conference. A handful of key staff were sworn to secrecy as plans were laid to give him time to leave Westminster for Heathrow, fly to Edinburgh, take a taxi home and close his front door before giving MPs, peers and the media 15 minutes’ notice that Simon Hughes, as party president, would make a personal statement about Sir Menzies at the Lib Dem headquarters in Cowley Street, Central London.

“The one thing he did not feel like doing was a big confessional press conference or being door-stepped or filmed walking out of Westminster, at Heathrow or in Edinburgh,” another senior Lib Dem said. “He wanted to do television interviews at home later, in a dignified way, rather than face shouted questions. That would not be a nice way to finish.”

News had begun to leak out when, at 6.10pm with Sir Menzies safely at home, journalists were summoned to Cowley Street. The party’s federal executive committee, its ruling body, was having a scheduled meeting in a Commons committee room. Sir Menzies sent apologies and Mr Hughes left during the meeting, telling members he had to give an interview.

Having announced the leader’s resignation, Mr Hughes returned and relayed the announcement. Lord Rennard, the party’s chief executive, then asked members to approve a two-month timetable to elect his successor. The procedure needed little revision, having been used to elect Sir Menzies in March last year. Few would have predicted that they would need to dust down the rule book again so soon.

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