Ahead of her summit with French President Emmanuel Macron today, Mrs May looked set to spark controversy over committing more cash to border controls in Calais as payment to keep the arrangement going.
The Prime Minister is set to hold a mini-summit with President Macron at the Army’s officer training school at Sandhurst where the two will agree a wide-ranging deal integrating defence and security arrangements.
The two will also strike an agreement on a series of other areas including sharing in the cost on a space mission to Mars and bringing the Bayeux Tapestry on loan to Britain where Home Secretary Amber Rudd is pressing for it to be put on display at Battle Abbey in Hastings.
Ahead of the meeting the Prime Minister emphasised that it showed that Britain will be able to leave the EU and have an excellent relationship with Europe afterwards on a wide range of areas.
While Brexit is not formally on the agenda, sources close to the Government believe it is a sign that Britain can expect to get a deep and comprehensive trade and security deal with the EU over the next year with President Macron touted as the bloc’s de facto leader.
Mrs May will say: “Today’s Summit will underline that we remain committed to defending our people and upholding our values as liberal democracies in the face of any threat, whether at home or abroad.
“But our friendship has always gone far beyond defence and security and the scope of today’s discussions represents its broad and unique nature.
“And while this Summit takes place as the UK prepares to leave the EU, this does not mean that the UK is leaving Europe.
“What is clear from the discussions we will have today is that a strong relationship between our two countries is in the UK, France and Europe’s interests, both now and into the future.”
Among new arrangements between the two countries will be a deal to step-up co-operation on shared threats.
This will include the UK bolstering fight against terrorism in Africa sending three Chinook helicopters to help French operations in Mali.
There will also be £50m of humanitarian aid to save lives in African countries suffering conflict, epidemics and natural disasters.
The Home Office is to help key partners in Africa to tackle immigration crime.
Meanwhile, France is to commit troops to UK-led Nato battlegroup in Estonia in 2019 to help combat the threat from Russia.
The five heads of the British and French security agencies will also meet all together for the first time while the political leaders meet to agree a plan to work together operationally.
A Government spokesman said: “Recent terrorist attacks across Europe underline the scale of the cross-border challenge we face in keeping our citizens safe. We will work together to deepen and enhance cooperation on law enforcement, security and criminal justice, to improve the safety of citizens across Europe and to strengthen our internal security capabilities.
“We will continue to work on the French-British Action Plan that Prime Minister May and President Macron signed in June 2017 including continuing to strengthen our cooperation to ensure that the internet cannot be used as a safe space for terrorists and criminals.”
The 35th summit between the countries will also see the agreements broadened to cover the full Anglo-French bilateral relationship including prosperity, innovation, science and education including support in teaching French and more school exchanges.
As well as attending the Summit the Prime Minister and French President are expected to have a private lunch and attend a reception at the Victoria and Albert Museum in the evening.