He has made a career out of lying 

Dear Sir, — Boris Johnson lies.
You can find out how much he lies by checking here: boris-johnson-lies.com The cynical among us will say all politicians lie but Boris Johnson has made a career out of lying.
As the prime minister he continues to lie.
He avoids scrutiny. He misleads us about where he got a £15,000 holiday and when he is confronted, he forgets where the money came from.
Investigations into Russian interference in our election and potential financial misconduct are pushed under the carpet.
He surrounds himself with second rate yes-men and women.
He gets his ministers to chant on television the lie (falsehood) that he will build 40 hospitals and makes them complicit in his lie (falsehood).
He lies (doesn’t tell the truth when he says) that he has Got Brexit Done when as we all know it’s only just begun.
Perhaps the biggest lie (falsehood) of all was the financial benefits that would accrue from Brexit.
In fact, according to the independent US financial institution Bloomberg, Brexit has so far cost us £130bn — and that figure increases daily.
No-one can say with a shred of honesty that Brexit will have a financial upside for a generation — if then.
His social and political life continues to be beset by scandal and incompetence.
Does anyone remember the failed Boris Buses, the failed Boris Island, the failed Garden Bridge, the failed cable car across the Thames and the failed Olympic site negotiations? He was a failure as foreign secretary.
Now he proposes a bridge from Northern Ireland to Scotland across a storm tossed strait and a sea trench full of bombs to a town in Scotland with no discernible road links to the rest of the UK.
It’s pure fantasy — a bright shiny thing to dazzle the unthinking.
But though we know all this, like the mini-me Trump that he is, he still enjoys support and a great deal of power. This is because we’d rather be told comforting lies than unpalatable truths. We would rather repeat fact free slogans than think for a moment about the complex reality of our situation.
We have become like children in a nursery believing in fairy tales about the evil EU and the brave knight who saved us.
We have become infantilised.
It doesn’t bode well for the future of the country. — Yours faithfully,

JEREMIAH