Fiennes will address delegates on May 25, at the close of the conference, which takes place in Southampton from May 23.

Fiennes, who served in the British Army for eight years, including a period on counter-insurgency service, was the first person to visit both the North and South Poles by surface means and the first to completely cross Antarctica on foot. In May 2009, at the age of 65, he climbed to the summit of Mount Everest.

Andy Harmer, senior vice-president membership and director Clia UK & Ireland, said: “We are thrilled that we have Sir Ranulph confirmed to address delegates at the conference. He’s a truly awe-inspiring character with incredible tales to tell, and it will be a privilege to be able to hear them first-hand.”

The three-day event will feature a trade fair on May 23 and a full day of conference and networking sessions plus a gala dinner on May 24.

The conference will close on May 25, onboard Princess Cruises’ Royal Princess, with Fiennes’ speech, followed by the opportunity to look around the ship.