A postcard for her first birthday, containing an unkept promise, was all Freda ever had of the father she never met. “My very sweet darling, just a line to wish you all happiness and many many happy returns on your birthday. I shall be with you on your next one and then we shall have a lovely party for my little daughter. Be a good girl till I come back. From your loving Daddy with lots of kisses xxx.”

Lance Corporal Frederick Palmer, 32, born in Chingford, Essex, was serving in the 54th Canadian Infantry battalion during the first world war when the battle of Amiens broke out in August 1918. Hit by a shell burst on the first morning he died two days later from wounds to his head and elbow. His 19-year-old wife and his daughter, aged 18 months, were left to mourn for him in Canada, to where Palmer had migrated.

Theresa May and Prince William, along with descendants of those who fought, will be among 3,000 people at a commemorative service in Amiens cathedral to mark the centenary of the first day of a battle which ushered the war’s end. May will read an extract from the War Memoirs of David Lloyd George 1917-18.

On 8 August 1918 an allied tanks and infantry attack – with raids from 1,900 French and British planes, at that time novel in their coordination – swept over the western front, dragging the first world war out of the trenches and smashing German morale.

General Erich Ludendorff, leader of the Germany army, described the battle’s first 24 hours, during which the allies advanced an average of 6.8 miles, taking about 15,000 prisoners, as “the black day” for his forces. The armistice was signed 100 days later. There were 75,000 German losses and 46,000 allied casualties.

Pat Bates, 61, Freda’s daughter, and granddaughter to Palmer, said the commemoration would be “a funeral for him that I can attend”.

“She missed not having a father,” Bates said of her mother, who was born two months after Palmer had departed for war and died aged 91. “There weren’t any letters, or at least my grandmother didn’t keep any letters, for my mother. All she had was the death telegram, the death penny [a memorial plaque given to the families of those who died] and the postcard.

“She treasured the card all her life. My mother was the least sentimental woman I knew. She got rid of all our toys and clothes, everything went, nothing was kept. But a picture of him in the kitchen and the postcard meant everything,” Bates said.

“My grandmother was a bit of a wild woman, and I think my mother regretted never having a father, providing a stable family life,” Bates said. “I treasure the card now. It might sound maudlin but it is in my bedroom besides a picture of my mother, and a miniature grandfather clock I had given her. I just want to honour him.”