Macquarie, which previously owned Moto, is reported by Sky News to have agreed a deal to buy Roadchef from Antin Infrastructure Partners.
City sources said on Thursday that a deal was likely to be announced in the next few days.
The major deal comes as motorway services station operators look to exploit the transition to electric vehicles, which present casual dining brands opportunities for longer dwell time
Roadchef is the third-largest motorway services area (MSA) operator in Britain, behind Moto and Welcome Break.
It is led by Mark Fox, former CEO of Bill’s, MD of Starbucks and MD of Pizza Hut UK & Europe.
Brand concessions include Costa Coffee and drive-thrus, McDonald’s, Leon, Chozen Noodle and Krispy Kreme.
According to Antin’s website, Roadchef has a 22% share of the market by number of sites, with 30 locations across the UK serving 52m visitors annually.
Antin initially invested in the business in 2014 in a deal reported at the time to be worth about £150m.
The sale is understood to be to Macquarie’s asset management arm, which runs money for third-party investors.
The Australian banking group previously owned Moto, selling it to the universities pension scheme USS in 2015.
A spokesman for Macquarie declined to comment.