Four months after Mr Cameron toured the continent to persuade fellow leaders to back wide-ranging EU reform, French diplomats are still scratching theirs heads. They are wondering whether a written wishlist will materialise during Mr Hollande’s stay at Chequers, the UK prime minister’s country residence in Buckinghamshire.

“Until we see a 10-page document laying out their proposals, it’s difficult to know concretely what they want and what they mean,” a French government official said. “This 10-page document must be somewhere, but we have yet to see it.”

The comments reflect mounting impatience in Europe over Mr Cameron’s reluctance, so far, to go beyond general principles ahead of what is expected to be a fraught negotiation process that will test the EU’s willingness to keep Britain in the union.

France is “listening with concentration”, the French official said. “Without worrying — but without euphoria either.”

Although technical talks have been under way in Brussels since July to explore options for Britain’s EU reform negotiation, the British have shared nothing on paper, much to the frustration of some EU capitals and officials.

Mr Cameron has been clear about some broad requests, which are categorised in four so-called “buckets”: sovereignty, competitiveness, fairness and welfare reform.

The British premier knows that his desire for “full-on treaty change” to enshrine the reforms will be problematic, but Mr Hollande and Angela Merkel, German chancellor, have indicated they were open to the idea of a “differentiated Europe” to accommodate groups of countries moving towards greater integration at different speeds.

But Mr Cameron has yet to flesh out a precise wishlist that can be transformed into a workable package and tested with other EU leaders.

British officials are loath to show their hand too early for fear the reforms will be picked apart by the “EU out” campaign and portrayed as insignificant. People familiar with the process expect it to be a month or two at the earliest before a more precise set of demands is circulated.

Officials are still aiming for a deal by Christmas. But, given the amount of preparatory work required on a package, some involved in the talks are beginning to fret that the British unwillingness to play their hand will hamper the effort to build a watertight package. “They are nowhere, and we don’t have that long,” said one senior EU official.

A Downing Street spokesman said: “The PM made the Elysée one of his first ports of call as he embarked on this renegotiation and the PM set out then the reforms we are seeking in four key areas.

“Today’s meeting at Chequers is an opportunity for the PM to update President Hollande on progress in the technical talks and to further discuss how we can work together to secure these reforms.”

“The timing has been somewhat disrupted due to more urgent matters,” said a French diplomat.

Mr Cameron is alive to the danger of complacency about Britain’s EU referendum among other leaders. In conversations with other leaders he is pressing home that he is willing to walk away from a deal should it fall short of what he would need to confidently campaign to remain in the EU.

While at Chequers, where Mr Hollande will stay until Wednesday morning, the French socialist president and his host may find it easier to discuss the state of play in Ukraine and Syria, also two topics on the agenda.

On Syria, the leaders are planning to “compare notes” and envisage ways to exchange intelligence and co-ordinate possible air strikes targeting the Islamic State of Iraq and the Levant, known as Isis.