When Vince Cable became leader of the Liberal Democrats in 2017 – almost by default, as one of the few left standing – he deserved it. His had been a career defined by his party colleagues failing to harness his talents, and at last he had secured its top job. But last week he announced he would resign in May, at a point when it is likely the Lib Dems will have to step up: either for a decisive election or a people’s vote. For a mere two-year leadership span, it already feels like he has hung on far too long.

Cable’s political life really started when he became a Labour councillor in 1971, and then defected to the newly created SDP in 1982. The impression he made on colleagues at that time was that of an unassuming team player, a man nerdily enthusiastic about the details of national policy and disinclined to throw his weight around. But if this was useful to those around him it did not boost his career. It translated as a lack of charisma, an impression not helped by his reserved manner and slightly nasal voice. When he eventually stood for the Lib Dems in 1992, in Twickenham, the entirety of the party’s resources went instead to Jenny Tonge, who was standing in Richmond (she quit the party in 2016 over alleged antisemitic comments). He was not viewed by colleagues as a future star – he was instead something of a “supporting character”, “never one of the first 11”, or just “the bald bloke”.

But Cable refused to admit defeat – a crucial talent for any budding Lib Dem – and eventually won a seat in the House of Commons in 1997, where he proceeded to steadily increase his majority. It wasn’t until the banking crisis of 2008 that he started to shine – he had continuously berated then prime minister Gordon Brown over house prices and consumer debt in the run up to the crash, and won a reputation for having predicted it. He started to get on television more, and journalists would ring him up not so much for a Lib Dem take as an expert one.

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But this development was not welcomed by Nick Clegg and his team, by then in charge of the party. Instead, Lib Dem sources say Cable was “resented and feared”, seen as a threat to Clegg’s leadership as someone with the potential to form a separate power base. Once Clegg had won some attention of his own after his triumphant TV debates in 2010, Cable, some recall, was firmly pushed into a corner in an attempt to focus the media on the party leader. And when the Lib Dems made it to government, a place where Cable’s careful policy thinking could have been of particular use, he was “undermined” by colleagues who didn’t work with him.

Facebook Twitter Pinterest Vince Cable, when he was a Lib Dem MP, at the opening day of the 2006 Liberal Democrat conference in Brighton. Photograph: Martin Argles/The Guardian

So when Cable became Lib Dem leader 2017, the oldest leader of a major political party since Winston Churchill, many saw it as justice served. By process of elimination he was the most recognisable Lib Dems – and still an asset to a fragile party. Younger colleagues were fond of him: a kindly figure who enquired about their lives and bothered to ask even the most junior staffer what they thought.

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He had his faults: he took direction badly. One reporter remembers agreeing on a line ahead of an interview with him, only for Cable to refuse to say it, despite repeated prompts. A furious press officer later texted him the quote anyway. He got bogged down in detail, tinkering with small flaws in policy ideas rather than finding ways to force them into the public eye. And he is far too slow – “He takes a long time to do things like sign-offs – he gets distracted very easily”, says one former staffer – and tends to pick up, then abandon ideas week to week.

None of this would have mattered had he been leader, say, when the Lib Dems were in the coalition government, or when their greatest hope was to gradually recover some territory. But Cable got the job at the very time he was least suited to it – when what the party needed was not a sensible caretaker but a dynamic leader. He would be good at leading them through lean times, but the overall impression of his leadership is now one of an opportunity missed.

It was then a bad misstep to announce his resignation in September last year, but not the date until last week: it drew energy from the party, and set the Lib Dems back in their preparation for any elections on the horizon. The delay was so that he could reform the party – now finalised – and bring in a supporter scheme so that new members could influence policy. But to prioritise this project in the era of Brexit seems like vanity – especially when, according to colleagues, it could easily have been completed without his guiding hand. It was not as though the candidates now lining up to be considered for his succession, such as Layla Moran, Ed Davey, and Jo Swinson, were not available six months ago either. It is to be hoped that the next leader can finally revitalise the party.

• Martha Gill is a political journalist and former lobby correspondent