Theresa May has arrived in Paris for talks with president Emmanuel Macron on plans to stop the internet being a safe space for terrorists.
The Prime Minister flew to the French capital after breaking off from negotiations with the Democratic Unionist Party to shore up her minority government following last week's disastrous election results.
Her host is riding high from spectacular successes in the first round of parliamentary elections last weekend, with the second round expected to deliver an overwhelming majority for his En Marche party at the end of this week.
Dressed in a grey jacket and black trousers, Mrs May was granted a guard of honour as she arrived at the Elysee Palace to be greeted at the door with a kiss on both cheeks by Mr Macron ahead of a working dinner.
The pair were later due to watch the France v England football friendly international at the Stade de France, where crowds are expected to sing God Save The Queen and observe a minute's silence in honour of the victims of recent terror attacks in the UK.
The gesture of solidarity comes after English football fans sang the French national anthem at Wembley following terror attacks in Paris in 2015.
Under plans being developed by Mrs May and Mr Macron, internet companies such as Facebook, YouTube and Google could be fined if they fail to remove extremist propaganda and terrorist material from their platforms.
Speaking ahead of her visit, Mrs May said she and the president were determined to ensure the internet could not be used as a safe space for terrorists and criminals.
The UK and France are to develop plans to create a new legal liability for tech companies which fail to take action against unacceptable content.
And the two countries will lead joint work with internet giants to explore the potential for new tools to identify and remove harmful material automatically.
Mrs May said: "The counter-terrorism co-operation between British and French intelligence agencies is already strong, but President Macron and I agree that more should be done to tackle the terrorist threat online.
"In the UK we are already working with social media companies to halt the spread of extremist material and poisonous propaganda that is warping young minds.
"And today I can announce that the UK and France will work together to encourage corporations to do more and abide by their social responsibility to step up their efforts to remove harmful content from their networks, including exploring the possibility of creating a new legal liability for tech companies if they fail to remove unacceptable content.
"We are united in our total condemnation of terrorism and our commitment to stamp out this evil."
Mrs May and Mr Macron will press tech companies to move forward urgently with the establishment of an industry-led forum to develop shared technical and policy solutions to the problem, as agreed by leaders of the world's most advanced economies at last month's G7 summit in Italy.
Home Secretary Amber Rudd and French interior minister Gerard Collomb will meet in the coming days to drive the agenda forward.
Britain's top anti-terror policeman, Metropolitan Police assistant commissioner Mark Rowley, echoed political concerns that terrorist material is too easily accessible online.
Writing in the Times, Mr Rowley said: "We need communications and internet-based companies to show more responsibility.
"It is too easy for the angry, violent or vulnerable to access extremist views, learn about attack methodologies, conspire on encrypted applications and then acquire equipment to kill, all online.
Mrs May was accompanied to Paris by Home Secretary Amber Rudd.