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Former UK Prime Minister Sir Edward Heath has been called "completely asexual" by one of his closest advisers. But what does that mean?

At least seven police forces nationwide are carrying out investigations linked to child abuse claims involving Sir Edward. This week, one of his closest advisers sprang to his defence.

Lord Armstrong of Ilminster, principal private secretary to Sir Edward during his time as prime minister, has said that he never detected even "a whiff of sexuality" in the life of the late Tory leader.

Questions were raised over Sir Edward's bachelor life as early as the 1970s. But his biographer Philip Ziegler has concluded that Sir Edward was actually almost completely asexual. But what is asexuality and how many people are asexual in the UK?

People who are asexual do not experience sexual attraction. Asexuality is a sexual orientation - it's not a choice like celibacy.

The asexual community has been growing since the early 2000s when forums and groups such as the Asexual Visibility and Education Network (Aven) appeared online.

It's estimated that 1% of people in the UK identify themselves as asexual but research is still limited, says Matt Dawson, lecturer in Sociology at the University of Glasgow. But although asexual people are often talked about as a group, members of Aven are keen to stress that there is a lot of diversity.

"People tend to assume things about asexual people," says George Norman, an asexuality activist and student at the University of York. "But there is a huge range of romantic orientation."

Norman first identified as asexual about a year ago. He explains that some asexual people do have romantic relationships. "It's important for everyone to realise that sex and romance are not necessarily the same thing," he says.

"The two can be distinct."

Dawson and his colleagues spent two years interviewing 50 asexual people about their lives and they found a whole range of experiences. "In no way was this a group that was lacking in intimate relationships," he points out. "Some will have sexual partners but that might be because they think it's because of the good of the relationship or just because they want to try it."

It can be a common experience, adds Norman. "Admitting that can help a lot of people realise that they are on the asexual spectrum."

There are still problems with the wider acceptance of asexuality. A study suggested that asexual people were viewed more negatively than people with other sexual orientations.

But there are signs that this is changing. "You do get negative reactions but in general, especially amongst young people, it's increasingly positive," Norman says.

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