If what matters most in a Trade Minister is business expertise, then he is the ideal choice.

The announcement yesterday that BT's impressive chief executive Ian Livingston is to leave his job to become a Junior Minister was clearly regarded by the Prime Minister as something of a coup. Going by Mr Livingston's track record, he does indeed have prodigious talent.

There are arguments to be made against the granting of peerages to political outsiders merely to allow for them to be made Government ministers. If democratic accountability is to be maintained, then it is clearly desirable that ministers should be chosen from the elected House of Commons, not the unelected House of Lords; what is more, it does not automatically follow that ministers will be more effective if they have professional experience in the field they are dealing with. A Minister without prior experience in his brief might more easily be guided by the wider concerns of the British public, unfettered by interest group bias.

However he or she might also be prone to errors of judgment without the fine detailed understanding that comes with years of experience in a field; that is why there is a strong case to be made for making expert outsiders junior ministers, answerable to a more disinterested Secretary of State. Mr Livingston fits the bill perfectly. To get the best from his new appointee, however, David Cameron must be clear about what he expects and be prepared to allow Mr Livingston to exercise some of the bold spirit of innovation he showed at the helm of BT.

The transition from businessman to Minister can be fraught, as the experience of past appointees demonstrates. Performing a policy role is one thing, but being a politician is quite another.

Some of the five ministers brought in by Gordon Brown in 2007 as part of his "Government of all the talents", epitomised the challenge.

Among them was the former director general of the CBI, Digby Jones, appointed Minister of State for UK Trade and Investment. He moved on after only 16 months and later declared that being a Junior Minister was "one of the most dehumanising and depersonalising experiences a human being can have. The whole system is designed to take the personality, the drive and the initiative out of a Junior Minister".

His contemporary Lord Malloch Brown, a former UN deputy director general who was made a Minister in the Foreign Office, found his pronouncements at times caused tension between him and his political colleagues.

In other cases, the past activities of expert outsiders have given cause for concern; the outgoing Trade Minister Lord Green has been dogged by the findings of a US Senate investigation that his former bank, HSBC, did not take sufficient action to prevent money laundering during his time as chief executive and chairman. Caution should be the watchword when deploying experts in ministerial roles.

Above all, if the Government is to benefit from the input of talented outsiders, it is essential that such ministers are both supported and listened to.