Thompson will attack Sky tonight during his Mactaggart lecture speech at the Media Guardian Edinburgh International Television Festival. Thompson will point to the vast scale of Sky and its influence over the UK broadcasting industry. He will compare the £2 billion the Corporation spends on programmes with the estimated £100 million Sky spends on original UK content. This is despite the BBC’s annual £3.6 billion licence fee being smaller than the £5.3 billion Sky earned last year. The BBC Director General is taking the gloves off and going on the offensive tonight, telling staff in a recent email that “it’s time to take on some of the BBC’s critics head-on”. Last year, News Corp director James Murdoch used the lecture to delivering a withering attack on the BBC, describing its scale as “chilling”.

Tonight’s keynote speech is seen as make-or-break for Thompson, who faces growing unrest among BBC staff. BBC employees are currently being balloted on whether to take strike action over plans to make their pensions less generous. And they smell double standards when top BBC managers opt to stay in London while the rank and file are forced to move to Salford, near Manchester. The BBC is moving more production to the north of England in order to stop the Corporation being such a metropolitan broadcaster.

In a nod to the challenges faced by the BBC’s commercial rivals, Thompson will call for the loosening of broadcasting regulations.

Among the great and the good of broadcasting gathered tonight in Scotland will be culture minister Jeremy Hunt and Pinewood Shepperton chairman Michael Grade. Controllers from all the major UK TV channels will be discussing their channel highlights.

This is a big public-speaking test for Thompson, who comes across badly in one-to-one interviews. He may be an intellectual but in person he mumbles and peppers his speech with lots of “you knows.” PD James, the octogenarian British crime author, demolished Thompson when she cross-examined him during BBC radio’s flagship Today news programme. Frankly, I’ve been appalled when listening to Thompson at how inarticulate he is. This from a man who’s paid £835,000 ($1.3 million) a year partly to enthuse staff with his vision for the BBC.

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