The sway exerted over the British government by US-domiciled media magnate Rupert Murdoch came to light on Monday when The Guardian newspaper exercised its right under the new Freedom of Information Act to view files showing the pressures applied by Murdoch and his henchmen on the Blair administration.

The Australian-born US national and his UK lieutenants sought and obtained private assurances from ministers that he would be able to purchase UK terrestrial channel Five if he so wished. The lobbying was at its most intensive in 2003 when the new Communications Bill was in passage through parliament.

This resulted in the insertion into the bill of what was widely termed the "Murdoch clause" - an amendment that reversed the prohibition of newspaper proprietors from owning a terrestrial television channel.

The clause seeped into the bill after News Corporation and BSkyB representatives gained face-to-face access to ministers on no fewer than six occasions during a crucial five-month period.

These meetings were hitherto unknown either to parliament or the public. Even now, the related documentation is said to be heavily censored.

However, it is widely believed that the decisive factor was intervention from Downing Street after Murdoch called in person on the UK prime minister.

Despite fierce protests from consumer groups and politicians of all shades - including former film-maker Lord David Putnam, one of the Blair administration's most senior representatives in the House of Lords - the bill became law in July 2003, albeit with some minor cosmetic strings attached to the "Murdoch clause".

The Blair administration and its Conservative forerunners have habitually genuflected before Patriarch Rupert, ever conscious that his four UK national newspapers command over 37% of the nation's readership - and exert considerable influence on electoral results.

The Sun, Britain's best selling tabloid with daily sales of over 3.3 million, is the strongest weapon in Murdoch's political armoury and is notorious for its front page banner headline after the Conservative Party (with The Sun's support) narrowly defeated Labour in the 1992 general election. This proclaimed (probably correctly): 'It's The Sun Wot Won It!'

A BSkyB spokesman insisted Tuesday that its executives had merely been "seeking clarification" of the government's plans in 2003: "We have stated then and since that Sky is not intending to buy channel Five. We are very insistent on that point."

But other students of Murdochian tactics are sceptical of Sky's disclaimers. Granville Williams of the Campaign for Press and Broadcasting Freedom said, after studying the newly released files, that Sky's lobbying indicates "they certainly do have some interest in the acquisition of channel Five, although they know it would be foolish to state this publicly until they are ready to make a move".

Data sourced from MediaGuardian.co.uk; additional content by WARC staff