Only one in 10 companies surveyed recently by the accountancy firm BDO Binder Hamlyn now think civil servants and politicians make suitable outside directors. Much more attractive, said the respondents, were executives with top-level management experience.
Nevertheless, former Conservative ministers do generally find City directorships easy to come by. So Lord Wakeham, John MacGregor, John Patten and Mr Brooke should not give up hope. They might, like Lord Parkinson, be chosen by a smallish, often strife-torn company - in his case the quarrying firm Starmin - to lend credibility. Or as with Norman Lamont, their former employers - in his case NM Rothschild, the merchant bankers - may just take them back.
Or, as in the cases of Lord Young at Cable and Wireless, Lord Tebbit at British Telecom and Peter Walker at British Gas, they might be hired because of their knowledge of government and, in particular, the way government regulates the utilities.
Mr Brooke founded the UK arm of Spencer Stuart in 1961. 'He's always said that he's been on extended leave since he first went into the Cabinet in 1979, and we've kept in touch consistently since then,' said a director. 'I imagine that once he's had some time to think about things, he could be back here in a senior advisory role.'
Tim Stephenson of Stephenson Cobbold, a recruiter of non-executive directors, said a leading factor in hiring ex-ministers was their background. 'If he's been an investment banker or something in the past then he's got some real value and is not just a name.'
On this basis Mr MacGregor, a former director of the investment bank Hill Samuel, stands a good chance of re-employment. He could also be of use to a transport company after pushing through the railway privatisation bill.
Lord Wakeham, a chartered accountant and former director of a number of companies, is strongly tipped to take up a City post. Mr Patten, previously an academic, is considered least likely of the four to venture into the City. He receives royalties from published books and was once an editorial adviser to the publishers Harcourt Brace Jovanovich.
Mr Stephenson estimates that the going rate for a non- executive spending 14 days a year at a company is between pounds 10,000 and pounds 18,000 a year. Non-executive chairmen, however, might hope to earn pounds 35,000 or more.
The trouble with non-executive directorships, following the implementation of the Cadbury Code on corporate governance, is that such jobs can be quite onerous. 'Most companies aren't just looking for names on letterheads any more,' said Mr Stephenson. Instead, they want people who can be watchdogs and might serve on the audit or remuneration committee.
'The requirement of a non- executive director is much more time-consuming than it was,' said Clive Reay, a partner at BDO Binder Hamlyn. 'Previously the watchdog role was low on the list, with advisory work a higher priority; now it is the other way around.'