After years of refusing to respond to questions about his citizenship and eligibility to be a member of parliament, Tony Abbott has finally confirmed that he renounced his British citizenship.

The ousted prime minister chose Friday, as Canberra was reeling from the shock resignation of Greens senator Scott Ludlam, who never renounced his New Zealand citizenship and has now admitted he was not entitled to run for office.

Mr Abbott released a copy of a letter, dated January 5, 2015, from UK Visas & Immigration as proof that he gave up his British citizenship some 23 years earlier, in October 1993.

Mr Abbott was born in London in November, 1957, and arrived in Australia as a three-year-old when his parents decied to return to Sydney.

He was elected for the first time in March, 1994 – six months after renouncing his UK citizenship.

The release of the letter appears to have been prompted by a tweet from another foreign-born senator, native New Zealander Derryn Hinch, who tweeted the apparent end of Mr Ludlam’s political career “should re-ignite the Tony Abbott dual citizenship debate. When did he renounce Britain?”

Mr Abbott’s response came just two hours later, settling one long-running mystery but giving birth to another: Why did Mr Abbott keep the information to himself for so long?

In 2015, a mere two weeks after Mr Abbott received his letter confirming he was no longer British citizenship, Western Australian Labor MP Terri Butler wrote to him on behalf of amateur journalist and self-proclaimed “pain in the arse” Tony Magrathea, who had long been promoting doubts Mr Abbott was a bona fide member.

On Friday, when Mr Abbott finally released the document, he appeared to enjoy rubbing conspiracy theorists’ noses in their own speculations.

Mr Magrathea was still not entirely convinced, tweeting that he was waiting on further confirmation from UK authorities.

And Mr Magrathea wasn’t the only social media maven unhappy that the citizenship rumour was untrue.

Another Twitter user immediately tweeted a doctored version of the Abbott letter attesting that he was highly regarded for his tight buttocks. Another wit suggested the delay in putting the rumours to bed was due to Mr Abbott needing to master PhotoShop software.

And just as Malcolm Turnbull has learnt about deposed prime ministers, some rumours are just too seductive to ever be entirely refuted.