The 58-year-old singer was romantically linked to the late royal during the 1990s, following the collapse of her marriage to Prince Charles, but during an interview on 'Watch What Happens Live with Andy Cohen', the 'Run to You' hitmaker remained coy about the speculation.
The host said to him: ''There are many rumours that you and Princess Diana were once romantically involved.
''Her butler said that he used to sneak you into Kensington Palace. How would you characterise your relationship with Princess Diana?''
The '(Everything I Do) I Do It for You' hitmaker replied, cheekily: ''Great friends. And she didn't sneak me in, I would just roll up.''
Andy subsequently asked whether they were ''friends with benefits'', and Bryan answered: ''She was just ... we were good friends.''
Later, the 'Heaven' singer shared some X-rated details about his personal life, revealing that the one and only time he took a picture of his penis was when he had the image framed and sent to Sir Elton John.
The Canadian star - who has been in a relationship with digital artist Alicia Grimaldi since 2009 - insisted: ''That was the first and only time.''
Bryan also revealed the chart-topping Brit - who is married to David Furnish - was happy to have received such an unusual gift.
He shared: ''When I gave it to him he said, 'I'm going to change that frame'. Now it's in gold. I think it's on his mantelpiece.''
Meanwhile, Bryan previously explained that one of his biggest hits, 'Summer of '69', is actually about sex.
Bryan admitted that a significant proportion of his fans had misconstrued the meaning of the track, which was released in 1985.
He explained: ''A lot of people think it's about the year, but actually, it's more about making love in the summertime. It's using '69 as a sexual reference.''
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