The widow of a Royal Navy officer took the chance to say thank you in person to the Duke of Cambridge for sending her family a "touching" letter of condolence when her husband was shot on a nuclear submarine.
Gillian Molyneux, from Wigan, described the Submariners' Remembrance Service and Parade in central London as an "emotional" day for her family.
Her husband Lieutenant Commander Ian Molyneux, 36, was killed by Able Seaman Ryan Donovan while HMS Astute was docked in Southampton in 2011.
The mother of four, who attended the service with her sons Jamie, 18, who is an officer's cadet and Arron, 16, who is a royal marine cadet, laid a wreath on behalf of submariners' widows.
She also has a daughter Bethany, 10, and son Charlie, seven.
Lt Cdr Molyneux was posthumously awarded the George Medal for his bravery.
Mrs Molyneux revealed that William had sent a personal letter of condolence.
It arrived in April 2011 as hundreds of mourners were to attend her husband's funeral and around the time of William's wedding.
Mrs Molyneux said it was "touching" to receive such a heartfelt message at such an important time.
Lt Cdr Molyneux was shot dead on board submarine HMS Astute while tackling a junior sailor who went on a rampage with a gun.
His actions saved the lives of several other naval officers.