The appointment was revealed today by the Department for Culture, Media and Sport, with the reviews set to consider whether the BBC is acting in accordance with assurances given at the time its digital services were approved.
The individual reviews will include market impact assessments. Ofcom will also contribute to the review process. The findings from the final reports will feed into the current review of the BBC's Charter.
Gardam quit Channel 4 in 2003 for what he said at the time were "partly personal reasons". He had worked at the broadcaster for five years. Before that, Gardam spent 20 years at the BBC working as an editor on programmes including 'Panorama' and 'Newsnight', before leaving to join Channel 5 briefly.
He is charged with reviewing the BBC's new digital radio services including 1Xtra, BBC 6 and BBC 7.
Barwise is professor of management and marketing at the London Business School. He will look at the television channels BBC Three, BBC Four, Cbeebies and CBBC.
Tessa Jowell, secretary of state for culture, media and sport, said: "The BBC has wholeheartedly embraced the digital revolution. But while licence-fee payers rightly expect their major public service broadcaster to be at the forefront of a rapidly changing broadcasting ecology, they also expect the government to ensure that the corporation fulfils its public service remit. These reviews will help us ensure that balance is being struck."
At the same time as the reviews were announced, the BBC said that its digital services may have been responsible for bringing 1m households into the digital television fold.
Citing successes such as 'Little Britain' and 'The Alan Clark Diaries', the BBC said that its digital television and radio services are delivering distinctive and original public service content to UK audiences and are on track to meet all conditions of their approvals.
The corporation made the comments as part of its submission to Jowell for the review.
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