The leader of the Welsh Liberal Democrats, Kirsty Williams, says it was she - and that it was the Lib Dems' coalition partners who insisted on the explicit link.
Her version of events is - to put it mildly - disputed at Westminster.
As I reported last month, the initial offer from the UK government had strings attached. Those strings were later cut after the Welsh Lib Dems threw their toys out of the pram.
But that was only after the referendum link had apparently been agreed by the deputy Prime Minister (and Lib Dem leader) Nick Clegg and (Lib Dem) Treasury Chief Secretary Danny Alexander.
There are even suggestions from Conservative sources that senior Lib Dem ministers wanted to go further - and require a Welsh government commitment to campaign for a "yes" vote in that referendum.
But Kirsty Williams has presented the proposed link as a dastardly Conservative plot, telling us: "I do not think it is reasonable for the Tories to say you can only deal with Wales's under-funding if you have that income tax referendum.
"That's why I blocked that announcement when that was being proposed from London to make sure that's not the case."
She may have opposed the explicit link but so, I'm told, did Welsh Secretary Stephen Crabb. It appears they were both on the same side of the argument arguing against senior figures in their own - and each other's - parties.
Coalition 2.0 anyone?

Martin Hamilton's body was discovered by a dog walker in woodland near West Calder on 17 December.
The 53-year-old, who was from Glasgow, was released from prison in September 2014 but was sought by police in April for breaching the terms of his licence.
Police described him at the time as "potentially dangerous". His death was being treated as unexplained.
Hamilton was nicknamed the Blackhill Butcher, after the Glasgow housing estate from which he operated.
He had been on the police's most-wanted list before he was jailed in 2000 over a string of charges including drug dealing, torture, abduction and sodomy.
Hamilton was sentenced to a minimum of nine years in prison after being found guilty at the High Court in Inverness.
The case was moved 200 miles from Glasgow amid fears that witnesses could be intimidated. Hamilton had evaded justice on 12 previous occasions when witnesses were too terrified to testify.
In court, a sickening picture emerged of how Hamilton, also known as the Fat Controller, entrapped young men with offers of drugs.
Two young drug addicts were imprisoned in a Glasgow flat, stabbed through the cheek and had boiling water poured over them.
Another attack in Edinburgh included an attempt to cut off a victim's finger.
Passing sentence, judge Lord Kingarth said: "You showed yourself capable of taking sadistic pleasure in the infliction of pain and the inspiration of real terror over long periods. You pose a substantial danger to the public."
When Police Scotland issued an appeal to find Hamilton in April they said he may be dangerous and urged members of the public not to approach him. A further appeal was made in June.
In October, an appeal was made on the BBC's Crimewatch programme and the Crimestoppers charity also offered a reward of Â£2,000 for information leading to his arrest.
Det Supt Kenny Graham said the site near West Calder where the remains were found would stay closed off or several more days "whilst we complete further searches and specialists carry out their work".
The nearby B7105 will also remain closed.
Det Supt Graham said: "My condolences go out to the family of Martin Hamilton, who have had to receive such devastating news so close to Christmas.
"A team of officers is dedicated to this inquiry, so we can seek to give them answers as quickly as possible.
"We are continuing to conduct examinations with various scientific experts to establish exactly when and how Mr Hamilton died, and to ensure any evidence available can be captured from the scene and from the remains themselves."
Who blocked an attempt by the coalition to tie a new funding deal for the Welsh government with a commitment to hold a referendum on income tax powers?
[NEXT_CONCEPT]
Human remains found in West Lothian last week have been identified as one of Scotland's most wanted men.