Lord Greville Howard - a friend of Prince Philip's - described the royal as highly intelligent and a natural leader who had a great sense of duty. 

He tells Sky News the Duke of Edinburgh was "delightful company, very well-read, intelligent and charming - and it was always enjoyable to spend time with him".

He describes him as a "great unsung hero of our time" because of his sense of duty.

"He always took second place to Her Majesty" despite having a very strong personality - not the easiest thing to do."

Lord Howard adds: "He never gave way to anything he felt like doing - he always fulfilled his duty."

Philip was a "natural leader", so despite being the Queen's consort, his "natural inclination was to take a leading role".

"He approached his role as consort with a sense of duty and obligation - and he had what the Queen has... because they are privileged they also have obligations."

As an example of their sense of duty and obligation, Lord Howard referenced when the Queen and Prince Philip stood in the rain and cold on a boat for her Diamond Jubilee river pageant.

Lord Howard says Sandringham was Philip's favourite place.

He says the duke was living in Wood Farm towards the end of his life - a farmhouse set in a secluded corner of the Sandringham Estate in Norfolk - and where Lord Howard spent the most time with him.

"He was just a wonderful companion," he says, adding the duke was "highly knowledgable about so many subjects - not many know he was a wonderful painter. 

"He invented the hooves for carriage riding - he was intelligent enough to do that," he adds. 

"I knew him at Sandringham best and that's where I would say he was happiest - evidence of that is that he retired there. I would say he was happiest there."

Talking of Philip's notorious sense of humour, Lord Howard says Philip didn't joke much, but would rather "making amusing comments, which I would enjoy".

"You never felt nervous with him because he was such a delightful person - and you always know where you were with him," he adds.