The former Chief of the Defence Staff Admiral Sir Michael Boyce has died at the age of 79.
Lord Boyce was the First Sea Lord from 1998 to 2001.
He was then appointed Chief of the Defence Staff – the last First Sea Lord to hold the position of Britain's military chief before Admiral Sir Tony Radakin's appointment last year.
He advised the Government on the deployment of UK forces in Iraq and retired in 2003.
He became a crossbench peer in the House of Lords and was made an honorary Admiral of the Fleet in the Queen's Birthday Honours in 2014.
Paying tribute to Lord Boyce, the First Sea Lord Admiral Sir Tony Radakin, said: "I am very sorry to hear of the passing of Admiral of the Fleet Lord Boyce, who has died peacefully after a long illness.
"Of all his many achievements, Lord Boyce was most proud to be a submariner.
"His quiet determination and focus under pressure represented the best of the Silent Service, and served him throughout an extraordinary career where duty and loyalty to his country was always utmost.
"His integrity as Chief of the Defence Staff will remain an example to all those who aspire to lead," he ended.