The Lib Dems are watching and waiting for the Brexit deal to unravel – under Vince Cable, they'll be able to take action

Cable believes that Jeremy Corbyn will disappoint his younger voters when they realise he is supporting Brexit

The former Business Secretary is due to replace Tim Farron as leader of the Lib Dems next week (Reuters)

In a valedictory interview with BBC Radio 5 Live today, Tim Farron pointed out that he was the first Liberal Democrat leader in 12 years to increase the party’s number of MPs at last month’s election. Unfortunately, it only went up from eight to 12.

The Lib Dems expected to win 30, or more, when Theresa May called the election. But Farron’s signature policy, a referendum on the EU exit deal, attracted not the 48 per cent but only seven per cent of the electorate. At times he looked out of his depth. He revealed today that he decided to resign only two weeks into the seven-week campaign. He was slow to calm media frenzy over whether he regarded homosexuality as a sin because of his evangelical Christian views. No one suggested he was homophobic, but his instincts looked out of time to potential Lib Dem voters – including in seats (like Cambridge) the party should have won. The Corbyn surge swallowed up other liberal voters. The anti-Brexit message bombed in the South-west, a former Lib Dem heartland.

Farron can rightly claim to have saved a party that dropped from 57 to eight seats in 2015, when it faced an existential crisis. Under him, membership has risen from 40,000 to 103,000. It has “left intensive care,” as he put it.

Next Thursday, Sir Vince Cable will be anointed Farron’s successor. Although the Lib Dems criticised May’s coronation a year ago, they will have one of their own because no one is standing against Cable. After the baby-faced Farron, the party will unmistakably have a grown-up in charge. Cable is 74, though he looks younger and is likely to escape the nasty ageism that destroyed Sir Menzies Campbell’s leadership. Cable does not lack energy: in the election, he was sometimes up at 5.30am to do breakfast TV, and spent hours knocking on doors to regain the Twickenham constituency he lost in 2015, before doing a public debate in the evening. Some Lib Dems expect Cable to step down after a few years in favour of Jo Swinson, the party’s new deputy leader. But he may have other ideas, and want to lead the party into an election.

Cable will reject calls from Lib Dems who want the party to ditch its second referendum pledge. But he will likely put it on the back burner rather than centre stage, which only attracts accusations of being a Remoaner and trying to overturn last year’s referendum. Instead, he will focus initially on the risks of May’s hard Brexit, which becomes more apparent by the day. Cable has credibility on the economy; he was the “sage of the credit crunch” after predicting the housing market collapse and banking crisis, and served as Business Secretary in the five-year Coalition. (Fascinating fact: the Lib Dems have more former Cabinet ministers on their frontbench – Cable, Sir Ed Davey and Alistair Carmichael – than Labour, which has only Nick Brown, its Chief Whip.)

However, Cable has assured Lib Dem members he will not abandon the party’s unique selling point on Brexit. “The referendum promise was two years too early,” said one Lib Dem insider. The tide might just be turning in the party’s favour after May’s election disaster. Philip Hammond and David Davis are trying to soften Brexit. Opinion polls suggest people might now prioritise economic links with the EU over controlling immigration. If there are signs that many are having second thoughts, the Lib Dems’ referendum promise could be shouted from the rooftops again. If the Brexit deal looks a bad one, there might be a Commons vote on a referendum. That could offer the best chance to stop Brexit.

The Lib Dems might then get some delayed credit for Farron’s policy. Cable told the Parliamentary Press Gallery this week that the Lib Dems are in a strong position to “break through the middle”. He argued that May’s deal with the DUP has trashed David Cameron’s 10-year effort to “detoxify” the Tory brand. He said Jeremy Corbyn offers implausible “Venezuelan socialism” and will disappoint his younger voters when they realise he is supporting Brexit.

The task for the Lib Dems is to prevent the next election being a re-run of last month’s, when 82 per cent voted for either the Tories or Labour and many seemed to think they had to choose one of two extremes. Yet voters did not give either main party a mandate, so there is a gap in the market. Under Cable, the Lib Dems will have a better chance of filling it.