It is tempting to dismiss the Lib Dem conference as a political non-event. Conducted almost entirely online, it failed even to offer the party’s dwindling membership the benefits that accrue from getting together and sharing policy ideas.

With just 12 MPs, it has little clout in Parliament just a few years after it was part of a coalition government and calling many of the shots. The decline has been rapid and steep. Sir Ed Davey, the party leader, did deliver his speech yesterday before a small live audience of invited participants but the largely remote format reinforced the impression of the Lib Dems’ political irrelevance.

But its capacity to damage the Tory party in particular, even from such a low base, is considerable, as was seen with victory at Chesham and Amersham earlier this year. Overturning a 16,000 Conservative majority will have given many more vulnerable Tory MPs pause for thought. 

There is a tendency to deride the Lib Dems as a party that stands for nothing but that is precisely why it is dangerous. It can adapt its policies at by-elections to exploit local grievances. At Chesham and Amersham, the successful Lib Dem candidate opposed the HS2 rail link even though the official party position is in favour. The Government’s planning reforms are deeply unpopular in the shires and the Lib Dems can be relied upon to oppose any development even while claiming to favour an increase in house building.

Sir Ed is the latest Lib Dem leader to claim his party can overturn the Tory majority, a triumph of hope over experience if ever there was one. But it poses a more direct threat to the Prime Minister because it unsettles MPs worried about their seats. They need to be given less cause for concern.