How Kate's granny helped foil Hitler: At Bletchley Park, the Duchess hinted at her relative's secret life as a code-breaker. Now RICHARD KAY reveals the inspiring true story

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She ended her days in a cosy four-bedroom detached house on the edge of a picture perfect Hampshire village.

It was a special place of happy memories where her grandchildren loved to play on a pirate ship in the big garden. 

Valerie Middleton had the added comfort of knowing the daughter of one of her sons was being courted by the future king. 

For Valerie Middleton was no ordinary granny. Bletchley-era photos show a vivacious young woman who, like Kate, smiled with her eyes as well as her mouth and had the same chestnut hair framing her face 

In those days, the fact that her granddaughter, Kate, was almost certain to be betrothed to Prince William was a family secret.

The world would know soon enough, but the 82-year-old mother of Kate’s father, Michael, was to take another Middleton secret to her grave.

It was her role at Bletchley Park, home of Britain’s wartime code-breakers. No matter how many times as a young girl the Duchess of Cambridge asked her paternal grandmother: ‘Granny, what did you do in the war?’ Mrs Middleton never breathed a word.

No matter how many times as a young girl the Duchess of Cambridge asked her paternal grandmother: ‘Granny, what did you do in the war?’ Mrs Middleton never breathed a word

This week, on a visit to a new exhibition celebrating Bletchley’s part in the D-Day landings 75 years ago, the Duchess spoke of her sadness that her grandmother could never talk about her wartime role at the secret base.

‘She was so sworn to secrecy that she never felt able to tell us,’ Kate told visiting schoolchildren during her tour of the estate near Milton Keynes. 

‘When she was alive, sadly she could never talk about it.’

What a story she must have had. We do know she was recruited with her twin sister Mary — Kate’s great-aunt — and they monitored diplomatic traffic from secret listening stations.

In this role, they witnessed one of the most extraordinary moments in Bletchley’s history. 

For the twins were on duty when a message was intercepted that Japan had surrendered.

This meant they were among the first handful of people — with George VI and Prime Minister Winston Churchill — to learn that World War II was over.

But, of course, they could not share the news with anyone.

Despite Valerie’s reluctance to talk about their role, the sisters’ vital work has been publicly recognised: Valerie and Mary, employed as Foreign Office civilians, have their names engraved on the Codebreakers’ Wall at Bletchley — the Edwardian mansion in Buckinghamshire is now a tourist attraction — which records the thousands who worked in signals intelligence between 1939 and 1945.

They worked in Hut 16, which originally housed boffins decrypting the Nazi Enigma machine. As Kate proudly told those pupils this week: ‘My granny and her sister worked here . . . it’s very cool.’

This week, on a visit to a new exhibition celebrating Bletchley’s part in the D-Day landings 75 years ago, the Duchess spoke of her sadness that her grandmother could never talk about her wartime role at the secret base

Bletchley’s war effort was celebrated in the Oscar-nominated 2015 film The Imitation Game about the brilliant but troubled mathematician Alan Turing.

In the war more than 10,000 people worked at Bletchley Park and at its linked locations, and 80 per cent were women. Churchill referred to the staff as: ‘The geese that laid the golden eggs and never cackled.’

Such a description would certainly have applied to Valerie and Mary Glassborow, who were only 20 when they arrived in early 1944. 

Just how the sisters, the daughters of a provincial bank manager, came to be part of the elite intelligence gatherers is still something of a family mystery.

Mary died from breast cancer aged 51 in 1975 while Valerie died in 2006 — and neither sister let on what happened during the war.

One relative told me: ‘It wasn’t just Kate, they never said a word to anyone. They had an older brother who they adored and they wouldn’t even tell him.

What a story she must have had. We do know she was recruited with her twin sister Mary — Kate’s great-aunt — and they monitored diplomatic traffic from secret listening stations. Wrens are pictured working on Bletchley Park, above [File photo]

‘All we ever heard was that they did secret work in England and were based in a country house. In those days, no one knew about the existence of Bletchley Park.’

What makes their story more remarkable is that after the war they married brothers.

Six months after Valerie’s wedding to former RAF ace Peter Middleton, Mary married his older brother, Anthony.

Since her engagement to Prince William, much has been made of the line of strong, indomitable women Kate is descended from.

There is her mother Carole, who started her Party Pieces business on the kitchen table; her other grandmother Dorothy who set the family on the road to prosperity and a great-grandmother who was determined to end the clan’s coal-mining tradition. 

But all those are on the maternal side. Surely the Glassborow women from her father’s side must also now be included?

For Valerie was no ordinary granny. Bletchley-era photos show a vivacious young woman who, like Kate, smiled with her eyes as well as her mouth and had the same chestnut hair framing her face.

The Duchess of Cambridge, pictured centre, with Bletchley veterans Elizabeth Diacon, Georgina Rose, Audrey Mather and Rena Stewart. Bletchley’s activities are said to have shortened the war by two years

The story begins in 1919 when the twins’ father, Frederick Glassborow, was demobbed after almost six years in the Royal Navy.

Frederick returned to his pre-war job as a bank manager. Working at the London and Westminster bank — today part of the RBS empire — he met Constance Robison and they wed in Marylebone in 1920. 

The couple loved travelling and when a job came up to manage the bank’s branch in Valencia, Spain, he took it. There, in 1922, the couple’s son, Maurice, was born.

Two years later, Frederick was working at a branch in Nantes, France, and the couple became parents to twins Valerie and Mary.

Soon, Frederick was transferred to Marseilles. The girls attended local schools and learned French. ‘They spoke like natives,’ recalls a distant cousin. This skill later made them attractive to the code-breakers at Bletchley.

Following convention, the twins went to boarding school in England — their brother Maurice was already at a Hertfordshire prep school. In the holidays, the children travelled back to France.

In the war more than 10,000 people worked at Bletchley Park and at its linked locations, and 80 per cent were women. Churchill referred to the staff as: ‘The geese that laid the golden eggs and never cackled' [File photo]

This idyllic life was shattered as war clouds gathered over Europe. At 17, Maurice joined the Navy. And Frederick remained at the bank until after the German invasion of France in May 1940.

What happened next is the subject of family debate. Kate’s biographer, Claudia Joseph, has written how he escaped on a ship as late as 1942 with the banks’ records stuffed into sacks.

‘As his ship was waiting to leave port, it was heavily bombed by German aircraft,’ Joseph wrote.

But family members recall being told that Frederick had gathered as many possessions as possible, loaded them into the family car and drove across France before boarding a boat to England.

‘It is the reason so few photos of Valerie as a child survive, so much had to be abandoned,’ says a Middleton source. Either way, in 1943, he took up a new post for his bank — in Leeds.

The twins had completed their education and wanted to help the war effort by learning office skills. They enrolled at Mrs Hester’s Secretarial College. With planning for the D-Day invasion in full swing, their linguistic skills made them ideal recruits for Bletchley. 

‘They were not maths geniuses so we don’t think they would have been breaking codes, but clearly it was important stuff,’ says the family figure.

Bletchley’s activities are said to have shortened the war by two years. On her first visit there in 2014, Kate met Lady (Marion) Body, wife of former Tory MP Sir Richard Body. 

She worked with Kate’s grandmother and great-aunt and told how Valerie, Mary and herself shared a ‘special moment’ on August 15, 1945.

Their superior officer came in and said: ‘Well done girls, a signal has been intercepted from Tokyo to Geneva and it’s the signal that the Japanese are surrendering.’

Lady Body said: ‘We sat there in complete silence before we were told to get on with our work.’ 

In those days, the fact that her granddaughter, Kate, was almost certain to be betrothed to Prince William was a family secret. The world would know soon enough, but the 82-year-old mother of Kate’s father, Michael, was to take another Middleton secret to her grave. She is pictured meeting young Lawson Bischoff at Bletchley Park

Asked if they heard the news before the King, Lady Body replied: ‘I should think about the same time. It was a great moment.’ 

She added that the Duchess bore a resemblance to her grandmother. ‘There is a likeness, in her hair colour, and possibly her eyes.’

She knew the twins well. ‘They were fun. We all got on. It was the only thing you could do, cooped up in here. We were all young girls together and we weren’t in uniform. I think we all had our 21st birthday on a night-shift.’

The sisters left Bletchley in October 1945 and joined their parents in Leeds. There they met the Middleton brothers, sons of a solicitor.

Peter and Valerie married in December 1946. Kate’s father, Mike, was born in 1949. Later, Peter became a pilot with BEA, and was selected to act as first officer to Prince Philip on a tour of South America in 1962. 

He was later sent a letter of thanks and a pair of gold cufflinks from Buckingham Palace. At his 90th birthday, he met Prince William, who was about to become engaged to Kate.

Valerie concentrated on raising four sons and welcoming their grandchildren to their Hampshire home. 

When Peter died four years after his wife, Valerie’s Bletchley secrets went, too. But nothing could take away from her achievements.

As a thrilled Kate said to Bletchley veterans this week: ‘Your families must be very proud.’