“If Johnson self-isolates, how will we know?” Thanks for that joke goes to Tim Walker, the gallant Lib Dem, who stood down in Canterbury to help Rosie Duffield. He defied then party leader Jo Swinson. Happily, Duffield won while Swinson lost her seat.

Walker’s quip ties in with Jeremy Corbyn’s labelling Johnson a “part-time Prime Minister” in their most recent Commons confrontation. It’s a charge that is likely to stick and is a useful bequest to his successor. Defining your opponent is a key skill for a political leader.

I’m a big fan of Michelle Obama and it brought a warm liberal glow when she declared at the 2016 Democratic convention “when they go low, we go high.”

Of course, she’s right. But when it comes to tackling Boris Johnson we have to play the man AND the ball. There is a pile of evidence that this a deeply flawed character, a liar in both his personal and professional life.

But we can perhaps leave it to journalists like Times columnist Jenni Russell to deal with the personal stuff. She asked “Why is BBC News sugarcoating the facts on Boris Johnson's children? Correspondent on news channel says he has 4 children with 2nd wife. It's public knowledge - after courts lifted order - that he has 5th with Helen Macintyre. Rumours of more.”

Professionally, he is a liar – sacked by two bosses; the editor of the Times for manufacturing a quote and by then Tory leader Michael Howard for denying an affair that was then confirmed as true.

Johnson just can’t help himself according to another ex-boss - this time Max Hastings of The Telegraph. Writing during the Tory leadership, he was scathing about his former employee’s “moral bankruptcy, rooted in a contempt for truth. ” Hastings adds, “his graver vice is cowardice, reflected in a willingness to tell any audience whatever he thinks most likely to please, heedless of the inevitability of its contradiction an hour later.”

Leadership frontrunner Kier Starmer is clearly relishing taking on Johnson.

He rejected the idea that his personality was a key part of the Tory victory. “No.” he told ITV’s Robert Peston, “We made him look good.”

Lest we forget, Johnson’s personal poll ratings are in negative territory, a fact obscured by Jeremy Corbyn’s utterly dire ratings. A bit of recent polling by Ipsos Mori gives Starmer positive figures, which would make him instantly more popular than Boris Johnson.

Over the next few years there will be plenty of policy failures and broken promises to fuel Labour’s campaign, but defining Johnson as “dodgy”, “sleazy”, or whatever adjective focus groups tell us fits best, is a vital task, not just for the new leader but for the whole party.

By Don Brind - Labour Movement for Europe Press Officer & Former BBC political correspondent

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