Otherwise he arrives at the British Gas offices on Grosvenor Road, Pimlico, by 8am at the latest (the 23-mile journey from Beaconsfield, Buckinghamshire, cannot take much more than 40 minutes at that time in the morning). He works through until 6.30pm, and three days out of five he attends a working industry dinner of some sort, some of which are far enough away to require the helicopter: last week, for instance, he was in Keswick.
The evenings he has free, he told the Investors Chronicle last week, he spends with his wife of 39 years, Joan, who, unlike many rich wives, has never made a single appearance in the social columns of the glossy magazines.
Weekends could not be duller. He does not entertain, but catches up on any outstanding paperwork and devotes his free time to his four children and two grandchildren, whose privacy he firmly protects. We do not even know their names and their ages. In Who's Who they are registered merely as "one s, three d''. Holidays are spent quietly en famille in Cornwall, although he did once go to Tuscany. Now there is a big trip to New Zealand planned, the exotic promise of which is causing much excitement.
As for a bit of self-interested corporate entertaining on the side - he does not even manage that. His great love is cricket, but he only found the time to go to Lord's for one day last year.
Who are his friends? According to a PR man who knows him, the few that he has he guards jealously. "I know that he is very close to some gas fitters, whom he met when he himself was a gas fitter. But it is something that he keeps very close to his chest. You would not find him in a French West End bistro carousing with them. That is not his style. He is a seafood salad man - he's been eating lightly recently - but Lobster Thermidor would be out of the question."
The central point about Cedric Brown is that he has worked for the same company, British Gas, for 44 years. It is scarcely surprising, therefore, that his friends are the gas fitters he met en route to the top. Nor is it really surprising he should find so little time to spend his vast salary.
"Unlike Peter Baring," says George Pitcher of Luther Pendragon, a media management consultancy employed by British Gas, "he is a nouveau businessman, who has to keep running to keep up. He has got to keep on top of the job. After all, he is not chairman [a post held by the rather flashier Richard Giordano], he is chief executive. There is a difference."
Cedric Brown does not have many high-powered friends. A friend of his says that he is really very isolated because, among the Establishment, "those on the right look down their noses at him, and those on the left regard him as a traitor".
Yet it is not just a question of time. If he wanted, Cedric Brown could easily jazz up his life. For example, he lists his interests in Who's Who as "sport, countryside, places of historic interest". According to Celestria Noel, social columnist for Harpers & Queen, many successful businessmen who have reaped personal enjoyment from music, sport or charity decide to put something back by joining a related board or chairing a fundraising event.
"If they themselves are too busy," she says, "then they get their wives involved. The person who chairs a big gala event always gets written up in the social column."
Last week, for instance, saw Sir Christopher Bland, erstwhile chairman of LWT, feature in the social columns as head of the committee for the Almeida Theatre's gala performance of Hamlet. Look him up in Who's Who and you find that in addition to his daily job he is chairman of Century Hutchinson Group, chairman of Life Sciences International, a governor of Prendergast Girls Grammar School, and he has had two works published.
While Bland's income is in all likelihood much bigger than Brown's, his extra-office curriculum is typical of many successful businessman, including those in public utilities.
David Simon, managing director of BP, whose salary was recently estimated to be £634,076, is on the council of the Foundation for Management Education; he is a member of the Sports Council and a Liveryman.
Likewise, Sir David Lees, the chief executive of GKN, who was reported recently as earning £330,386, is governor of Shrewsbury School, on the executive committee and council of the Society of Motor Manufacturers and Traders, and a member of the Audit Commission.
Now that Cedric Brown is in this league, he could afford at least one consultancy position and one charity. Even Christopher Walford, the Lord Mayor of London, who probably earns much less, has, according to Celestria Noel, hoved into the view of the social columnists because of his involvement with fundraising events for the British Heart Foundation.
Cedric Brown, by contrast, is not even a member of his local cricket club in Beaconsfield, let alone the MCC.
The National Trust had not even heard of him, neither had the organisers of the urban development scheme "Working for Cities", despite the fact that British Gas Properties is sponsoring their competition.
If he is not out and about socialising, it seems clear, it is simply because he is just not interested.
"Cedric Brown?" the Prime Minister's brother Terry Major-Ball asked. "I'm sure that his social life must be very different from mine." Mr Major- Ball is absolutely right. His is a lot more exciting.