DAVID Cameron highlighted the ongoing defence and diplomatic co-operation between the UK and France as he joined world leaders marking the anniversary of D-Day.
The Prime Minister said the two nations had faced a common enemy in 1944 and remained important allies 70 years on.
He said there had never been a more important time to underline their belief in collective defence.
"Just as British and French soldiers fought for victory against a common enemy on the beaches of Normandy, today France and the UK stand shoulder to shoulder against the threats of the modern world. We remain united against international terrorism and extremism - and in recent times our armed forces have served together in Afghanistan, Libya, Mali and elsewhere around the world."
Mr Cameron said the "shared hardship" of the Second World War had "forged our unique relationship and created a shared determination to work together for a safer, more prosperous future for us all".
He added: "That future is why so many of our servicemen gave their lives - and protecting the peace they fought for is the greatest way we can honour those who fell."
The 70th anniversary of the Normandy landings awakened poignant memories for Irene Ashton, 85, of Loxley Close, Clifton Moor, whose late husband Tom, who died two years ago, aged 87, was a D-Day hero.
Mr Ashton's father - also called Tom - served in the Royal Navy in the Great War and survived being sunk at the Battle of Jutland.
He decided Tom was a lucky name and so it turned out to be when his son also joined the Navy and was posted to landing craft duty on June 6, delivering American troops to the Omaha beach head.
Tom was so scarred by his experiences he never wanted to return to France for the D-Day reunions.
Mrs Ashton said her husband took part in two waves during the landings, first delivering infantry through the hail of bullets and shells. Then he returned with the tanks badly needed to complete the breakthrough.
He cheated death twice more during the Normandy campaign - once when his ship sailed into Cherbourg harbour before the mines were cleared. He also nearly walked into a minefield while exploring the French countryside - but a farmer yelled a warning just in time.
Mrs Ashton met her husband after he was demobbed. He had been given jungle warfare kit to fight in the Far East but Japan surrendered.
After the war, he worked on the Derwent Valley Railway. He was last station master at Elvington and later worked for Yorkshire Water.
The couple had five children, eight grand children, and two great grandchildren.
Mrs Ashton added: "He got on with everyone and was such a good father and husband. I wish he was still here.
"He would have loved to be around for the 70th anniversary. But he never did go back to France for any of the others. He said he could not stand to remember all those who had been killed or drowned."