Green’s Dictionary of Slang

gently Bentley! excl.

[BBC radio’s weekly comedy Take It From Here (1940–60), used as catchphrase by Jimmy Edwards (1920–88), addressed to Dick Bentley]

a general excl. of restraint, hang on! take it easy! not too fast! etc.

[[UK]London Calling 28 Sept. 21/3: 23.15 Dick Bentley in ‘GENTLY, BENTLEY’].
[UK] ‘Through Elland deep water’ on BBC Liverpool 🌐 Thank Providence too that things currently look a lot brighter for the Blues. Gently Bentley, let’s enjoy the ride.
[Aus]P. Carey Theft 249: Now it would be gently Bentley as they removed the Magna.