As any regular visitor to London knows, the capital's Tube system faces a constant battle to cope with record numbers of travellers. The network, parts of which date back to the 1860s, carries more than three million passengers a day and vast sections require major surgery just to maintain current levels of service.
A huge factor in these problems, trade unions argue, is a 30-year public-private partnership (PPP) agreement set up in 2003 between state-run London Underground and two companies: Metronet - which is responsible for running most of the trains and infrastructure - and Tube Lines, which provides maintenance services for trains and infrastructure on certain lines.
Whatever the political arguments for or against PPP agreements like this one, integrating two sets of staff from such different backgrounds throws up a variety of challenges, not least for HR.
The first thing to ensure, according to Sue Loseby, an HR consultant at PricewaterhouseCoopers, is that HR is involved in any discussions at a very early stage. Many areas of the public sector are heavily unionised, for example, so she advises HR to try to replicate the relationship during and after any transfer period.
There are also legal issues. Many PPP agreements are governed not by law but by binding deals that have been thrashed out with unions - often along the lines of the Transfer of Undertakings (Protection of Employment) regulations that affect mergers.
These have an impact on issues such as salary, pensions and holidays. But the retention of employment model - where some employees effectively work for the company yet are still employed by the public sector - confuses things still further.
Consequently, HR professionals from both public and private sector backgrounds have to familiarise themselves with a whole new set of legal practices.
In the case of Metronet, the situation was made even more complex by the fact that the 5,000 staff being transferred were joining a totally new company with no established HR procedures.
It was also forced to address skills gaps in key areas, such as project management, which would prove critical to delive