He's one of the UK's most high-profile public figures to come out as gay.

And 32 years after his own acknowledgement of his sexuality, Sir Ian McKellen is praising Elliot Page for announcing last month that he is transgender.

The two worked together on the 2006 Hollywood movie X-Men Last Stand and the British actor told Attitude magazine he's 'very happy' for Page.

Page played Shadowcat in Last Stand that came out the year before his starring role in the indie film Juno put him, then as Ellen Page, on the map.

McKellen, who starred in the X-Men films as Magneto, told the magazine that he is 'so disappointed' he failed to realize that the then teenage Page was struggling with sexual identity.

'I remember Elliot Page, in one of the X-Men, sat as close as we are now. And I had to speak when they'd finished, and I couldn't hear what they were saying. Nobody could hear what they were saying,' he recalled.

'So, I said, 'Look, if you can't speak up, would you mind when you're finished speaking, just dropping your hand so I know when you've finished speaking?'

He went on: 'And then they came out [as gay] years later and suddenly you couldn't stop them talking. You heard everything.'

McKellen, 81, said: 'I'm so happy for Elliot. And so disappointed in myself that I didn't detect what their difficulty was with communicating.'

'Everything gets better [when you come out] because you get self-confidence', he explained. 'You get better in terms of relationships, friends of all sorts, family, if you're lucky. And in my case, I think in every case, your acting is bound to change and improve.'

McKellen came out in 1988 as a protest against then Prime Minister Margaret Thatcher's section 28 that forbade local government and schools from 'promoting homosexuality'.