The first major issue is the restrictive covenants clauses in the candidate's original contract that say if you leave you cannot encourage, take or persuade another member of staff to go with you. Most contracts these days, particularly at senior levels, include such clauses. Recent experiences in the City suggest that investment banks are more than willing to pursue through the courts those who flout them .
Headhunters are also bound by 'no poaching' clauses, although it is harder for employers to make a case against them and they have less incentive to do so. But when an entire team leaves an established business, whether it is in equity research or corporate finance, it can have a devastating and expensive effect on the investment house concerned.
One veteran headhunter who has been responsible for some high-profile team moves says: 'It is incredibly difficult to pull off an entire team move. It is logistically extremely complicated. Either the whole team resigns on the same day or you go for the leader first. But then, if people follow, it is deemed to be the leader's fault.'
The team the leader wants to put up, however, is not necessarily the team the bank wants, which puts the headhunter in a tricky position. The leader may not be deemed by his future employer to be in a position to assess which of his team members he should want until he gets to his new job. But as soon as the bank lets one member of the team know he or she is not chosen, that person can become adversarial and foil the entire plan.
Another headhunter says: 'You have to pretend that each is the chosen one until the final moment. For a team move to be successful the best thing is for the leader to have a team that is entirely relevant to the new employer, and not to include extra people who are being hired just to appease the leader's wishes.' So a team leader who protects his colleagues against the cherry-picking of the future employer is unlikely to be doing them a favour in the long run.
Every team has a natural leader, and it is extremely important for this person to know and understand the mind-set of each individual on the team. A group of seven individuals ranked No 1 in their geographic sector recently moved from one major investment bank to another after the leader had lost his job following a merger. The others resigned in protest. Complicated contracts in locations across central and eastern Europe had to be sorted out and priorities decided.
The team leader says: 'We agreed a list of firms that we were going to approach. We decided we were not going to talk to anyone on an individual basis. There was to be no poaching and no dumping. A number of firms said they were willing to live by the rules and then immediately violated them. The one we joined in the end did exactly what it said it would.'
An important part of this move was that the relationship with the previous employer had already been severed, which makes it much easier to operate. The leader feels that there was a great deal of responsibility placed on him, and that the smooth workings of the move also depended to a large extent on his relationship with the headhunter concerned, the Rose Partnership.
But headhunters are often more concerned with their relationship with each member of a team as an individual than they are with the team as an entity. This is because they never really know which way their client - the employer - may jump.
A headhunter at one of the big four global search firms says: 'A team is just a collection of individuals with the common point of reference that they work together. They could have different aspirations and different agendas. If you treat them as homogeneous it can come unstuck anyway. It is better to treat them as a group of individuals who happen, in certain circumstances, to be moving together.'
He is in favour of team-building that is done in sequence very rapidly because it then becomes 'less of an issue'. Describing team moves as an organ transplant exercise that is not always successful, he says that employers who insist on importing entire teams fail to appreciate that they then import that team's culture as well. They also point out that if new employees come as a team, they tend to go as a team.
Headhunters say team moves should not be based on merger and acquisition models, for the contracts are ultimately handed out to individuals. Success can also depend on the team's size: while moving two or three people together may not be that hard, moving numbers from five to 15 becomes exponentially more difficult.
Ultimately, if you have worked together as a team for years, trust each other implicitly and know that you will only move together, you may have a chance to make a move en masse that works for you.
Employers be warned, however. Headhunters in the City shake their heads at the notion that team moves provide instant critical mass to a business, pointing to an old adage reworked - recruit in haste, repent at leisure.