McManus' biography offers a rounder picture of the late politician he had known personally for years.[Photo provided to China Daily]

McManus, who studied at Oxford University, began his career in the political section of a Conservative Party research unit. When he worked for Heath, one of McManus' tasks was to persuade him to write his memoirs. The former prime minister had to once return an advance from a publisher for being almost two decades overdue.

"The process was descending into farce. I said to him, 'Do you want me to do it?' He said, 'Yes' and I said, 'OK, but you must cooperate. I am not going to mess about,'" McManus says. "He didn't normally respond well to being told what to do but he eventually said defensively, 'Yes, of course'."

The autobiography, The Course of My Life, drafted extensively by McManus, came out in 1998 and was well received.

"The fact it happened at all got an extra star. It was worth a star for just happening."

After leaving Heath's employment, the writer stood for parliament himself as a Conservative candidate before working for the public relations company Bell Pottinger and others. He became a full-time writer in 2014.

McManus is now working on a political play about Heath, who was also a world-class yachtsman winning the Sydney to Hobart race in 1969 and an accomplished musician.

"I think there would be a lot of humor in it (the play) because I tried to get a lot of humor in the book."

One startling aspect of the biography is McManus' conclusion that he didn't actually like Heath.

"Somebody came up to me the other day and said he was moved to tears by the bit where I tried to decide whether I liked him or not. I respected him, even was quite fond of him but didn't naturally warm to him."

Heath, who died in 2005, remains a relevant figure in modern UK politics, especially since June's Brexit decision undid his greatest legacy of leading his country into the European Economic Community in 1973.

"He was Mr Europe, so Europe was always right even when it was wrong. He backed himself into a corner on the subject. It was frustrating for those of us who worked with him because he became intemperate on the subject."

McManus, who accompanied Heath on three visits to China, was not always enthusiastic about some of the food he was served up.

"Some of the things made him go a bit pale, especially the things that came bubbling up in the soup that might have been better left in the sea."

Heath's China connection continues to date. His house Arundells in Salisbury - one of only three 20th-century homes of British prime ministers open to the public - has been saved by an injection of funding by Beijing-based businessman Peter Batey, also a former political secretary of the late prime minister.

"I think he just felt like a big man in China. Every time I went with him - and he was an old man by then, without any real influence - he was treated with this sort of reverence by the Chinese," McManus adds.