Sky News understands that Aggreko has agreed a 400p-a-share offer for Crestchic, which is listed on the junior AIM exchange.

City sources said the deal was likely to be announced on Friday morning.

It is expected to value Crestchic at just over £100m, and will represent a roughly 15% premium to Thursday's closing share price of 356p.

Crestchic floated in 2006 and specialises in hiring and selling specialist power reliability equipment.

Its purchase by Aggreko will come nearly 18 months after the buyer was itself delisted from the London market following a £2.3bn takeover by I Squared Capital and TDR Capital.

Aggreko's business has performed strongly this year amid disruptions to power supplies in many of the markets in which it operates.

The deal will also represent a relatively rare corporate transaction during a year of subdued mergers and acquisitions volumes.

Centerview Partners is advising Aggreko on the talks.

Crestchic did not respond to a request for comment on Thursday evening.