On the go: Marsh & McLennan, the insurance broker and consultancy that owns Mercer, has announced it is to buy Jardine Lloyd Thompson for $5.6bn (£4.3bn) in cash.

The deal brings two of the largest pensions advisory businesses together at a time when market share of investment consultants and fiduciary managers is under intense scrutiny.

Mercer is one of the so-called 'big three' firms, which between them control between 45 and 49 per cent of the investment consultancy market by revenues, according to a recent investigation by the Competition and Markets Authority.

JLT is one of the CMA's anonymised second tier of consulting businesses, where the largest company controls 8 per cent of revenues. Its employee benefits division generated £320.2m in revenues in 2017. It is also the UK's largest administrator of private sector pensions.

The CMA found that the investment consultancy market was not highly concentrated, citing the fact that no company had a share of more than 20 per cent, and the three largest controlled less than 50 per cent. It is not yet clear whether the acquisition will change that.

It is also not yet known whether the pensions services offered by the two companies will merge or remain separate entities under one parent group.

Dominic Burke, group chief executive of JLT, said in a statement: "I am enormously proud of what JLT has achieved, founded on our people, our culture and our unwavering commitment to our clients. MMC is, and always has been, one of our most respected competitors and I believe that, combined, we will create a group that will truly stand as a beacon for our industry."

In a separate acquisition, listed pensions consultancy XPS Pensions announced it is to buy the assets of public sector administration provider Kier Pensions Unit for £3.5m.