Typically, "secondees" are assistant solicitors with two to eight years' post-qualification experience. But in one case at least, a managing partner is undergoing the experience. John Rink, of Allen & Overy, is spending part of his working time as acting head of the legal department at British Aerospace. He is backed up by another Allen & Overy partner, seconded full-time.
According to Martin Pexton, the firm's personnel director, around 20 of Allen & Overy's 280 assistant solicitors in the London office are currently on secondment.
The process carries several benefits, he says. "From the individuals' perspective, it provides a completely different outlook on work. It also helps them, and the firm, understand what the client wants, and it strengthens links with that client."
It could be argued that there is an element of exploitation in the arrangement; that the client is getting the same service at bargain prices.
"It doesn't usually work that way," Mr Pexton says, "The pattern is of a specific slot that needs filling for a time, for example at British Aerospace. If we did feel that the client was looking for cheap legal advice, we would resist and look at our level of charging."
But Charles Dodson, joint managing partner at Lovell White Durrant, is in no doubt that secondment is exploitative. He says that the past two or three years have seen a greater demand by companies for secondees, driven in part by the same cost considerations as their lawyers.
"Clients see it as a neat way of solving the problem," he says. "It is obviously cheaper than if they were billing the firm. But we place a huge emphasis on what the client wants. The advantage from our point of view is that it helps in cementing relationships. And it is giving our lawyers a chance to see the whole business from the other side of the fence, and increases their commercial awareness."
Clifford Chance has operated a formal programme of secondment for about 10 years. Greater efficiency is the key, according to Stuart Popham, the managing partner of the firm's banking and securities group. "We find it very useful to have lawyers with experience and a greater understanding of the client's business, both generically and of the particular institution," he says. "It helps the client to use our services more efficiently, and we get to know his individual demands. It gives us greater command of forward-planning and an easy access point. All in all it creates a better relationship."
One risk that goes with seconding valuable fee-earners is their defection to the client. Mr Popham admits to losing two or three lawyers in recent years, although in the first half-dozen years of the firm's secondment programme, no one decamped.
"Without exception our lawyers enjoy secondment," he says. "Some are confirmed in their desire to stay at Clifford Chance, others use the time to discover whether they do want to work in banking, for instance." Secondment is also used for pro bono assignments - work at a law centre, for example - for training, or for the advancement of international practice.
"One of our major objectives is the entire management of major transactions in foreign jurisdictions," says Charles Dodson of Lovells. "In some jurisdictions we can meet that demand by clients, but in others, where we have no offices, such as Germany or Spain, we need to have very close links with local law firms, so that we can satisfy the client that things will run smoothly. It is absolutely crucial that our firm is one entity - secondments play an important role in ensuring that happens."
Bruce Westbrook, a partner in the oil and gas sector at Cameron Markby Hewitt, describes his firm's use of secondment in terms of providing the client with what he wants.
"At the beginning of the Nineties, work was not raining in to law firms as it did in the Eighties," he says. "We have to work harder to look for clients, get alongside them, and deliver what they want in a way that is convenient to them - that is, to reach out to them."
Cameron Markby opened an office in Aberdeen two years ago, "purely and simply to be available on the spot to oil companies and contractors.
"A good number of large companies there have legal departments that get overstretched from time to time," Mr Westbrook says. "Part of our remit is to provide an overflow service, either on a one-off basis or with specialist skills not available in-house. We found that the client was saying: `We would like to have someone dedicated to us for three months.'
"Seconding people provides us with a very valuable way of discovering how the client works, how he uses lawyers, what areas we need to gear up for the future. Secondment is useful. It is not instantly profitable, although it provides a contracted income, but it fosters relationships with clients and helps us build our business."