To help electricity company Scottish Hydro-Electric merge with Southern Electric, Herbert Smith wheeled out its latest weapon, gamekeeper turned poacher Michael Shaw (pictured right).

Shaw, who co-led Herbert Smith's team with partner David Paterson, had only just returned to Herbert Smith in June after a two-year stint as joint secretary to the Takeover Panel and was able to bring his insights into how the takeover rules are applied to give the £2.7bn merger a greater chance of regulatory approval.

“It's a case of poacher turned gamekeeper and back again,” he said, adding that “many advisers can only guess at how the panel will react”.

He said his time at the panel also gave him a much wider network of contacts within the investment banking community, which would be useful for developing future clients.

“It was good to get stuck into such a high-profile deal so quickly,” he said. Although the deal was only a share-for-share merger with no cash premium offered, it was a complex transaction because of its sheer scale and the need to co-ordinate closely the regulatory and corporate work.

Herbert Smith is one of the leading law firms advising utilities. It worked on the original privatisation of the regional electricity and water companies and has been lobbying the regulators over the timetable for the introduction of electricity competition.

All the UK's privatised utility companies are consolidating rapidly in the run-up to the regulator-imposed deadlines and Shaw predicted a growing bonanza of work for utilities lawyers: “There is going to be a lot of jostling for position.”