Britain's Prince Harry speaks at the Commonwealth Heads of Government Meeting Youth Forum in London, Monday, April 16, 2018. (AP Photo/Alastair Grant, Pool)

Sir Elton John has praised Prince Harry for his "passionate" charity work and skill at putting people at ease.

The 'Rocket Man' hitmaker was first introduced to the 33-year-old royal by his late mother Princess Diana years ago and he's been overjoyed to see the prince's transformation from a "shy and sweet" youngster to a devoted campaigner for the issues he believes.

Writing for TIME magazine - who named Harry one of their most influential people - Elton revealed: "I first met an extremely shy and sweet Prince Harry at a private lunch at Kensington Palace, given by his mother Princess Diana for Gianni Versace and me many years ago. 

"What a joy it has been to see that young boy grow to inherit his mother's warmth, sense of humour and courage to stand up and champion the causes he truly believes in.

"Harry and I have bonded over a passionate desire to end the global AIDS epidemic, a disease for which his mother did so much important early work to fight stigma and build awareness.

"He is equally passionate when it comes to reducing the stigma surrounding mental-health issues--blowing a much-needed breath of fresh air into the British stuffiness that has kept vital conversations lurking in the shadows.

"The Invictus Games are his creation, and they give dignity and hope to injured armed services personnel and veterans by offering a spectacular and inspirational global competition in sport."

The 71-year-old singer went on to praise Harry for his skills at putting people at their ease, whatever the situation.

He added: "Prince Harry has that rare ability to walk into a room full of strangers and make everyone feel comfortable and at ease. 

"As he has grown in maturity, I have watched him take on these causes with the remarkable skill to see and communicate how it truly feels for the people he is trying to help."