Thursday saw some interesting twists in the London Mayoral election campaign, with the three main candidates publishing details of their tax affairs. They agreed to do this after a Newsnight debate on Wednesday evening, when Boris Johnson, Ken Livingstone, Brian Paddick and Jenny Jones all said they would disclose what they earned and how much tax they paid.

This in turn followed the explosive row which broke out between Boris and Ken during an LBC Radio debate earlier this week, with Ken accusing Boris of taking income from a TV production company, Finland Station. Boris memorably denied this, and later accused Ken of "f*****g lies" for making the claim in the first place.

On Thursday Boris Johnson and the Lib Dem candidate Brian Paddick published their tax details, in the form of PDF files from their accountants. Ken initially refused to do this, claiming that the only way to achieve "full disclosure" would be for all the candidates to reveal their total household incomes, not just their individual earnings.

This, said Ken, was because the tax avoidance allegations which have been constantly levelled against him also involve his wife, who was paid by the same company as him, Silveta Limited. She was apparently paid to type up Ken's memoirs, and like him would have been paid at the corporation tax rate of 20%, rather than the higher rate of income tax.

Ken was accused of stalling, and only after pressure from the other candidates and the media issued a PDF of his own - not from his accountants, although Ken's team claimed that's where the figures came from.

So with all three disclosures, what do we now know that we didn't before?

With Boris we've discovered that he earned £1.3m over three years, all of which was paid to him either directly as a salary - for doing his job as Mayor of London - or from freelance payments. These come from his work for the Daily Telegraph where he continues to be a columnist.

Critics of Boris claimed this high income explained why he lobbied for the 50p top rate of tax to be reduced - something George Osborne ended up doing in the Budget last month. The New Statesman points out that if Boris' earnings continued on their present level (assuming he's re-elected next month, of course!) - he would gain from the tax rate reduction by around £16,000 a year.

But the numbers back up Boris' claims - he has paid around 45% tax on his earnings, and none of them appear to have been paid by any company. Boris appears to be paying slightly less tax than might be expected, but he could have allowable deductions, like professional subscriptions, which would explain the discrepancy.

Brian Paddick finds himself in a similar position. His income has dropped markedly since 2008, when he earned around £130,000 in "other income" - presumably sales and advances on his own memoirs, "Line of Fire", which were published in the same year.

Since then he has relied increasingly on his police pension of just over £63,000 - he is taxed on that at 20% for the first £40,000 or so, and then at 40% thereafter. He had 'other earnings' of just over £13,000 - the details of what these earnings where are not given, but they could be subjected to different tax arrangements, depending on what they were.

According to Paddick's own website, the total tax paid as a proportion of his taxable income in 2010/2011 was about 29%.

It's when you turn to Ken Livingstone's tax affairs that things become less transparent, because Ken has been paid by a company - he makes no secret about that.

He says that the numbers he's published today came from his accountants, although unlike Johnson and Paddick there is no letterhead to corroborate this. That would be a cosmetic detail, were it not for problems with how the figures have been drawn up.

Clearly rushing to quell claims that he was stalling, Ken claims that he paid just under £35,000 in tax last year on a total income of £94,500 - an effective rate of 36%.

But there are some strange anomalies in the records - firstly in Ken's claim that he paid £11,000 in "corporation tax on dividends" - however dividends don't attract corporation tax, they attract income tax. This might be an honest mistake, but it is not one that any tax accountant worth their salt would be expected to make.

What complicates Ken's claim is that he does not say in those figures how much he has earned and left in his company, it only says what he has taken out the company. Companies House records for Silveta Ltd suggest that there's still a lot of money from Ken's income - paid into the company, not directly to him - which has not been paid out. This is going on the most recent figures available up until June 2010, when the company had assets of around £284,000.

This confusion has led to the claim that Ken's actual tax rate is actually only about 14%. Labour are trying to deny this and have issued a briefing document to be used by their staff.

What seems to be most damaging for Ken, though, is that he has reluctantly rushed out a set of figures which have only thrown up more questions than answers.

He hasn't broken any laws, but he's managed to switch the whole debate in this election away from policy and towards the financial dealings of the candidates.

Behind in the polls, and now tipped by the bookies to lose the Mayoral election, the Labour candidate appears to have come out of a week-long row - which he himself ignited - the loser.