Former PMs Boris Johnson and Rishi Sunak offer advice to incoming Andy Burnham

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As Andy Burnham prepares to step into the role of prime minister on Monday, an unusual chorus of advice has emerged from his Conservative predecessors, offering insights into the demands of the top job.

While Sir Keir Starmer has publicly declined to offer counsel to his successor, other recent occupants of No 10 have been more open, collectively stressing the immense time pressures Mr Burnham is about to encounter.

Writing in The Sunday Times, Rishi Sunak urged Mr Burnham to "soak up every second" of his arrival in Downing Street, reflecting on his own regret at not allowing himself "a moment of reflection".

However, once inside, Mr Sunak added that it was "imperative" for a prime minister to "have a plan" for using their time most effectively. This, he suggested, involves regularly engaging with MPs and driving "two or three" key priorities from No 10.

Mr Sunak concluded: "The constraints on your time mean it is vital you pick your priorities, and communicate them to Whitehall quickly while your stock is at its highest."

Amid speculation about Mr Burnham’s Cabinet picks, Mr Sunak also stressed the importance of appointing the “most able” ministers to the jobs that most mattered to a prime minister’s priorities.

While attention has focused on whether Ed Miliband or Shabana Mahmood will be chancellor, the former prime minister said it was the choice of foreign secretary that would be the most important.

He said: “Burnham wants to spend less time on international affairs than his predecessor did, but this will begin to be possible only if he has a foreign secretary who is sufficiently well known and respected on the global stage to stand in for him.”

But he suggested that this would only go so far, urging Mr Burnham to secure one-on-one meetings with other world leaders given “the extent to which personal relationships influence international diplomacy”.

Referring to his negotiations with the EU, he said: “We would never have got the Windsor Framework done if I had not built up a relationship of trust with Ursula von der Leyen, the European Commission president.”

Another of Mr Burnham’s predecessors, Boris Johnson, also offered the incoming prime minister some advice in an interview with Sky News’s Sunday Morning With Trevor Phillips.

Mr Johnson said he wished Mr Burnham “well”, but like Mr Sunak said he “hasn’t got much time” with a public “doomscrolling through prime ministers”.

He added: “He needs to get on and he needs to give investors in this country a sense of hope about it.

“And that means he needs to find reasons to buy British, get stuck in and he needs to stop the haemorrhage of talent.

“And he needs to think about what he’s doing on tax. And Labour needs to get a grip on spending.”