British officials hope to influence Donald Trump by exploiting his character and inexperience in office, a secret memo reportedly from the UK’s top diplomat in the US suggests.

The president-elect’s tub-thumping campaign that carried him into the White House revealed his “instincts”, Sir Kim Darroch, Britain’s ambassador to the US explained in a dispatch as the result emerged.

The populist, if extreme, pledges that stirred up support for the newcomer could be shaped by UK officials who have already laid the groundwork in Washington, Sir Kim suggested.

Nigel Farage the first UK politician to meet Trump since election

The memo, seen by The Sunday Times, said: “The president-elect is above all an outsider and unknown quantity, whose campaign pronouncements may reveal his instincts, but will surely evolve and, particularly, be open to outside influence if pitched right.

“Having, we believe, built better relationships with his team than have the rest of Washington diplomatic corps, we should be well placed to do this.”

Downing Street said it did not comment on leaked documents.

Whitehall was thrown into a diplomatic quandary by Mr Trump’s surprise election on Wednesday.

After years of frosty relations the UK faces the possibility of having to reassess its stance on Russia following the president-elect’s praise of Vladimir Putin.

The tycoon has also threatened to partially withdraw support from Nato and scrap a deal with Iran over nuclear weapons.

Meanwhile there are hopes for a fast-tracked trade deal with the US as Britain leaves the EU.

Concerns were raised over the health of the “special relationship” after it emerged Mr Trump had spoken to a series of leaders before calling Theresa May after his victory.

The Prime Minister was careful not to pick sides during the presidential campaign, but had previously said his comments on Muslims were “plain wrong”.

Meanwhile Boris Johnson, who previously said Mr Trump was “clearly out of his mind”, appeared to have adjusted his position and was keen to speak to Vice President-elect Mike Pence and congratulate the Republicans.