The extraordinary piece of television that was multi-millionaire Zac Goldsmith’s interview on Channel 4 News last week (if you haven’t watched it yet, do so here) has now spun out to see Croydon Central’s new MP, Gavin Barwell, having his election expenses investigated as well.

A report on Barwell and four other MPs, from across the political spectrum, is to be broadcast on Channel 4 News tonight from 7pm.

The C4 News investigation discovered that Barwell neglected to declare any payment for renting his office in Purley from the local Conservative Association (Purley is not even within Barwell’s Central Croydon constituency).

Electoral rules require candidates to declare rental charges, even if their party owns the property.

C4 News further reports that: “He also appeared to claim a £500 printing refund without including the original charge, which may have further reduced his costs.”

A Conservative party spokesman told C4 News: “We have been made aware that there is an anomaly in Gavin Barwell’s return. When the discrepancy was drawn to the attention of the Gavin Barwell’s agent, he realised his error at omitting two items of expenditure from the return and is taking the appropriate action.”

Ah. A “discrepancy”. That’ll be alright then.

As the Croydon Advertiser reported recently, Barwell’s election spending far outstripped that of any of the other parliamentary candidates for Croydon Central in May’s General Election.

Barwell’s spend was £34,685.76 – or £10,000 more than the next highest spender in Croydon’s elections.

Barwell has denied that his campaign received any special funding from his friend and former Tory HQ colleague Lord Ashcroft, the Conservative party deputy chairman and chief donor, a billionaire who pays no UK tax thanks to his non-domiciled status.

Barwell’s spending also included £738 for controversial letters, signed by Tory leader “Call Me Dave” Cameron, rubbishing Barwell’s predecessor as the Croydon Central candidate, Andrew Pelling, who this year stood as an independent.

Pelling has described the Cameron-Barwell letter “vile” and “lacking veracity”.

Of his former close colleagues in Croydon Tories, Pelling said, “I don’t know how Gavin and the Conservative activists who conspired in distributing such a letter can live with themselves.”

Even Barwell has attributed his high spend on the election in contributing to New Addington electing a Tory local councillor for the first time in 46 years, helping towards the Conservatives’ narrow majority on Croydon Council.

• For more detail on how multi-millionaire Zac Goldsmith, new Tory MP for Richmond Park, manipulated the limits of his election expenses to gain an advantage, and that explosive C4N video again, click here.