The High Sheriff of Hertfordshire, Richard Pleydell-Bouverie, said David had been killed in his tent on Saturday night in the remote Matusadona National Park where he had been a safari tour assistant.
"We have spent an awful night - we don't know the details," Mr Pleydell- Bouverie said at the family home in Kimpton, near Luton. "We are going through the most unbearable and appalling family tragedy. This is something we wish to come to terms with privately."
Staff from the British High Commission in the capital, Harare, are at the 338,000-acre reserve to help the investigation and David's mother, Victoria, is believed to have flown to Zimbabwe yesterday.
David, described by a friend as a "bright, genial young man with a taste for adventure", had recently extended his stay in Zimbabwe to work in the safari park whose publicity claims it has "the highest concentration of lions in Africa".
A Zimbabwe parks spokesman said: "It seems the young man was taken from his tent in an attack by a group of lions and killed in the darkness. The tracks indicated two lions in his tent and possibly others outside. What was left of the body was a little bit further away."
An ageing lioness thought to have led the attack and a male have been tracked and shot.
David, due home in October, was on a gap year before going to university. He had had a teenage dream of working in Africa and was employed by a company called Under Canvas in Africa.
The nephew of the Earl of Radnor, he has a sister 15, and a brother, 17.Reuse content