Queen star Brian May has gained his doctorate in Astronomy - 36 years after starting his thesis.
The rock guitarist, who abandoned his studies to pursue a career in music, was told of his success after taking a three-hour exam to discuss his work.
The 60-year-old, who handed in his 48,000-word tome earlier this month, said: "You can call me Dr May!"
The musician will be officially handed his PhD from London's Imperial College at the Royal Albert Hall next spring.
"I feel comfortable about using the title because I worked for this, and I'm going to be proud to call myself Doctor from now on," May, who lives in Surrey, told the BBC News website.
He also holds two honorary doctorates.
May said that his oral examination - or viva - was "very, very tough", but wanted his thesis to be scrutinised by academics.
"It's a bit like an album - you've got to live with it for the rest of your life, so you want it to be perfect," said the rock star.
May has been awarded a category two pass, which means he must make a few amendments to his work in the coming weeks.
The performer's thesis is entitled Radial Velocities in the Zodiacal Dust Cloud, and he has been in the Canary Islands to carry out some astronomical observations.
May said he is "very keen" to carry out some further research and added that "some pretty spectacular stuff" could be achieved.