Acquisition is the easy part. Getting people to work together is much harder.

When Chief Executives say ‘Our people are our greatest asset’, they are often met with a cynical response. In the case of failed investment banks, though, their people are their only asset. Banks don’t have much in the way of buildings or machinery. Once they go as deeply into the red as Lehmans and Merrill Lynch are, their only value is in the heads of the people that work for them. The skills and, critically, the relationships of their employees make up most of a failed bank’s residual worth.

This is what Bank of America wants from Merrill Lynch and what Barclays hopes to retrieve from the wreckage of Lehmans.

But when things go wrong at banks, the first people on the scene are headhunters. Ten years ago I remember friends at NatWest Markets and BZW telling me how the key talent was walking out of the door as people began to fear for their jobs. When a bank is in difficulty, other employers can pick up good people without needing to coax them away with such large packages. In effect, an ailing bank can be asset stripped by headhunters before it is even sold.

Fortunately for Bank of America and Barclays, the job market in the financial sector is not great so many of the assets they are buying will probably stay put and see what happens, at least for the time being. But even if the refugees are desperate for a new job, it still pays to treat them well and to plan their integration into the new firm, otherwise, at the first opportunity, many of the people so expensively acquired will leave, taking their expertise and relationships with them. Already, commentators are asking questions about how well Bank of America and Merrill Lynch will integrate. The Los Angeles Times points to the cultural differences between the two organisations:

There are vast differences between the two corporate cultures, and the deal was thrown together so quickly that potential land mines may have been overlooked, said Rob Hegarty, a financial services industry analyst.

“It’s far too early to call this a success,” said Hegarty, managing director at Tower Group. “I’m calling it ‘Heartland Meets Big City’ — and we know how most of those marriages end up.”

San Francisco’s Business Times reckons that BofA’s cost-sensitive Southern culture will not go down well with Merrill’s city slickers.

One can only imagine the reaction Merrill’s spendthrift New York workforce will have to receiving the first cost-cutting memo that routinely emanates from the bank’s Charlotte headquarters.

At times like this, firms need very good HR people to help manage these transitions in such a way that the cultural clashes are minimised and the assets from the acquired business don’t get the hump and head off down the road. There are some HR and OD people who know how to do this stuff and are really good at it. The trouble is, they too are scarce and very much in demand.

Whatever the bosses at BofA do, though, I hope they don’t make the Merrill Lynch people sing ‘One Bank’. I wouldn’t wish that on anyone - not even Wall Street investment bankers.