During the Afghanistan crisis last summer, Ben Wallace decided that he had what it took to be prime minister. He had suspected it before then, according to friends, but during the evacuation of Kabul the Defence Secretary came to a definitive conclusion.

His prediction that the Taliban would take Kabul had been proved correct, when other senior ministers involved had failed to see it coming. And as the desperate situation played out following the US withdrawal, he hit his stride.

His row with the then foreign secretary Dominic Raab over the fall of Kabul was a turning point for the way he saw himself, insiders say. Raab was caught off guard, on holiday. Wallace was on top of his brief, cancelling a weekend away, deploying British troops to the airport as the Taliban advanced, declaring that he had known ‘the game was up’ months ago.

He even defied public hysteria to speak out against the apparent diversion of military resources to rescue the cats and dogs of Pen Farthing’s animal sanctuary. While much of the establishment echoed public opinion in defending the airlifting of pooches alongside people, Wallace, a former captain in the Scots Guards, said he found it ‘upsetting’ and ‘not something I would be proud of’. He took a lot of stick from Farthing, a national hero at the time. It was almost six months later that an inquiry into the episode concluded he was right to be concerned. Foreign Office memos released in January suggested that, in the middle of the crisis, Boris Johnson had intervened after his wife Carrie and her animal campaigner friend Dominic Dyer had pushed for the government to help the dogs.

Crikey, I remember thinking at the time, this Wallace chap stood up to the vegans! We should not entirely scoff, therefore, at the idea that a minister whom few of us knew anything about until recently is being touted as a possible successor to Johnson.

With the Ukraine conflict uppermost in the public’s mind, the idea of a military man in No. 10 is certainly a comforting one. Perhaps the time has come for a soldier to take charge of our response to this chaos, seems to be what many are thinking, causing Wallace’s popularity to soar. Tory members, according to the latest survey, rate him at the very top of a long list of possible candidates, with Liz Truss second and Rishi Sunak at the bottom, the beleaguered Chancellor having bombed in the approval ratings since the revelations about his wife’s nom-dom status.

Wallace is undoubtedly as astute in military matters as one would expect of a former soldier who has served in Germany, Cyprus, Belize and Northern Ireland, where he was mentioned in dispatches in 1992 for an incident in which the patrol he was commanding captured an IRA unit attempting to mount a bomb attack against British troops. He was also injured in service – a punctured eyeball – so he’s obviously brave.

The problem is, for all his many fine qualities, Robert Ben Lobban Wallace can come across as a bit of a chump. That’s not really a criticism, more a statement about his personality type. These Sandhurst officer chaps can be a bit, well, full of themselves.

Public-school-educated, the son of a soldier in the 1st King’s Dragoon Guards who saw service in Malaya, a former ski instructor with the Austrian National Ski School… it’s all rather ‘bloody good bloke’-ish.

His attitude can seem a bit cavalier, to say the least. In the run-up to Vladimir Putin’s invasion of Ukraine, which to be fair he predicted, he complained that the European response to the mounting crisis had ‘the whiff of Munich’. And while his handling of Ukraine has been assured, he rather too enthusiastically boasted that Vladimir Putin had gone ‘full tonto’ and the British army could ‘kick the backsides’ of the Russians. ‘Well, hurrah and huzzah!’ one is tempted to reply, as if one were in the company of General Melchett in Blackadder.

Critics complain of the ‘mania’ of his ambition and the fact that there is something comical about his derring-do. He is always on manoeuvres, is the gossip in the Commons tearoom. He earned the nickname Captain Fantastic when he became a Member of the Scottish parliament and the Herald newspaper noted his relentless optimism.

His attack on the culture of heavy drinking at Westminster, while no doubt a serious topic, elicited raised eyebrows and gasps of hilarity from those who claimed Wallace was more than a little committed to being the life and soul of the party.

He plays the military card too enthusiastically. His picture on the government website was recently changed to one of him in a camouflage jacket to emphasise his war-leader credentials. During a visit to Arvidsjaur in Swedish Lapland last December, he put on a big black furry Russian hat similar to the one Margaret Thatcher wore during a visit to Moscow in the 1980s, as he announced that British soldiers must do more cold–weather training to be ready to face the growing threat from Putin. The fact that another leadership contender, Liz Truss, wore an identical fur hat two months later on a visit to Russia, in spite of a thaw in the weather, only heightened the sense of posturing.

And then there was that hoax call. How seriously can we take a minister who spends ten minutes on a video call with a Russian prankster posing as the Ukrainian Prime Minister, with all the security implications that potentially entails?

‘I need to speak to my Prime Minister…the principle is we will support Ukraine as our friend in the choices you make,’ said Wallace, striking an earnest tone, before the questions became so absurd he terminated the call and went on Twitter to complain about ‘Russian disinformation, distortion and dirty tricks’, which is a lot of words to say: ‘I’ve been had.’ The video has now been taken down from YouTube but if you google Wallace it is still one of the top items that comes up, and one suspects there is a chance it always will be.

That said, we should remember there was once hilarity about the fact that Theresa May fancied herself for the top job back in the early 2000s. The story went that she overheard someone in the Commons tearoom describing her as Thatcheresque, when what they had really said was ‘statuesque’. Nevertheless, having become enamoured of the idea, she did eventually become prime minister, and arguably not our worst one ever.

Another parallel, perhaps, is with the former Tory leadership contender David Davis, who made much of his SAS (Territorial) prowess when he pitched for the top job. But that is a cautionary tale. He fancied his image as an action man so much that he forgot to write his speech to the Conservative conference until the very last minute, leaving the way open for David Cameron to make a tub-thumping address without notes, setting him on an unbreakable path to victory.

Davis, it should be remembered, posed with girls in tight white T-shirts emblazoned ‘It’s DD for me’, allowing the impression that he was a hit with the ladies while being somewhat dismissive in comments about his long-suffering wife, Doreen.

Wallace married Liza Cooke in 2001, four years before becoming an MP, and has three children. She worked as a part-time parliamentary assistant in his office until 2019. They separated a year ago.

He is a Johnson loyalist and one of the original gang of supporters who urged him to stand for the party leadership when he was still mayor of London. He ran the PM’s first leadership campaign after Brexit, which crashed and burned when Michael Gove threw a wobbly. Wallace’s analysis of Gove was scathing: ‘Michael seems to have an emotional need to gossip, particularly when drink is taken, as it all too often seemed to be… UK citizens deserve to know that when they go to sleep at night their secrets and their nation’s secrets aren’t shared in the news-paper column of the Prime Minister’s wife the next day, or traded away with newspaper proprietors over fine wine.’ That is all very well, so long as Wallace isn’t going to trade secrets with any more pranksters on video calls, or get into any other bother.

The consensus about Wallace is he’s fundamentally decent. After the US withdrawal from Afghanistan he was asked: ‘Why do you feel it so personally, Mr Wallace?’ He replied with emotion: ‘Because I’m a soldier… because it’s sad, and the West has done what it’s done and we have to do our very best to get people out and stand by our obligations.’

When Johnson goes, one feels sure that if called on to serve, Captain Fantastic will stand by his obligations.