In September 2013, Peter Oborne wrote a piece in the Daily Telegraph in praise of Ed Miliband, calling him a brave and adroit leader. I remarked at the time that he was a columnist renowned for going against the grain of the newspaper for which he writes.

It is to his credit that he did so and was to the Telegraph’s credit that it hired him and published him for five years. He never subscribed to the paper’s large-C Conservative line on many subjects.

Indeed, he defies political categorisation because he is not a party man. To describe him as broadly rightwing doesn’t quite do him justice either. The well-spring of his politics appear very personal and, having made up his mind about something, he argues his position with great passion.

On the Middle East, for example, he called for Britain to back a Palestinian state in a column in October last year, having previously worried over what he has called “the pro-Israel lobby in Britain”.

He has argued the Conservative case for the Human Rights Act. He was one of the very few non-Guardian journalists to take Nick Davies’s phone-hacking revelations seriously in 2010 by presenting a Dispatches programme on the issue.

But he was noted for his virulent dislike of New Labour, particularly Tony Blair and his press aide, Alastair Campbell, for their political spinning. And he has been antagonistic to Britain’s membership of the European Union.

I ought to add that he wrote a disobliging piece about me last month, in which he claimed I was doing Labour’s dirty work. (I wasn’t, but let’s leave that to one side).

The point is that Oborne is a journalistic maverick. He is independently minded; he is unorthodox; he does not share any paper’s, editor’s or, more pertinently, any publisher’s, agenda. And he has principles.

Peter Oborne demands inquiry into Telegraph guidelines over HSBC Read more

He walked out of the Daily Express in April 2001 soon after Richard Desmond’s takeover, rejecting the opportunity to avail himself of a tax-free payoff.

In his years at the Daily Mail, from April 2006, he often wrote articles at odds with that paper’s overall opinion but its editor, Paul Dacre, appeared relaxed and there was a measure of regret when he quit to join the Telegraph in May 2010. (It is possible that he will return to a paper he calls “raucous and populist”).

At the Telegraph, all seemed fine until its editor, Tony Gallagher (“excellent”, says Oborne), was fired in January 2014. But we now learn, according to Oborne’s Open Democracy article, that he had registered his upset with the paper as early as April 2013 when he bumped into the Telegraph Media Group’s chief executive, Murdoch MacLennan, at Margaret Thatcher’s funeral.

People familiar with the situation tell me that Oborne was disenchanted for months, before he told MacLennan last December that he was resigning.

They made an agreement, which was not publicised, that he would serve his six months’ notice, staying on until the May general election. But he was later told his weekly column would be “discontinued”.

Oborne writes that he was prepared to go quietly. However, as anyone who knows him well will testify, he is not one to let matters drift. Anger festers within Oborne and often explodes.

It is entirely feasible that Oborne was so disgruntled he was looking for a way out that would make a big bang, and the HSBC business was the dynamite. Whether it was a coincidence or not, Oborne has certainly made out a persuasive case that the Chinese walls between advertising and editorial at TMG have been breached.

He revealed that a piece he wrote about HSBC’s closure of accounts held by British Muslims went unpublished because there was “a bit of an issue” with the bank. He also discovered that a story about HSBC by Harry Wilson, the former banking correspondent of the Telegraph, had been removed from the website.

A major story in November last year about HSBC setting aside more than £1bn for customer compensation was downplayed by the Telegraph, and Oborne pointed to other examples of advertisers being placated by editorial decisions.

Telegraph's Peter Oborne resigns, saying HSBC coverage a 'fraud on readers' Read more

According to Oborne, at a meeting with MacLennan, the CEO was unapologetic about the matter, suggesting that it was no big deal. But it is, of course. It is a very big deal indeed because it goes to the heart of a paper’s credibility. Readers will not trust a newspaper that withholds or censors stories to please advertisers.

Everyone in the newspaper industry knows that advertising is harder and harder to come by. We know also that TMG has been reporting a level of profits for several years that surpasses any other national group. How, we wonder, does it do that?

The implication of Oborne’s revelations is that part of its strategy involves pandering to big advertisers to the extent of curbing critical editorial content.

I imagine this is rare, but once one company gets away with threatening to pull its advertising unless negative stories are pulled then the word goes round. It opens the door to discreet deals. So other instances may have occurred that we know nothing about.

Oborne felt that the HSBC case was so blatant that it was impossible to ignore and it could have far-reaching implications. Frankly, I’m amazed that MacLennan would be party to such activities.

Many people throw mud at him, but there are very few newspaper managers who love the company of journalists as much as he does. He and I have fallen out several times down the years, but I haven’t lost my regard for him. This matter, however, is of a different order altogether.

I don’t think we have to look too far for the major culprits: Sirs David and Frederick Barclay. And they exercise their powers through David’s son, Aidan, who manages their UK interests.

In my only meeting with Aidan, during a brief, unhappy period as a Telegraph media columnist in 2006, he told me I should be writing more about the Telegraph’s success. The guy doesn’t seem to get journalism and, nor, would it seem, do his father and uncle.

Newspaper proprietorship gives unaccountable rights to owners. For once, the Barclays are being held to account. Oborne, the maverick, has shone a light on a dark reality.

