Remember the Chinook was not a ‘clean sheet of paper’ design concept, but the result of a line of designs from Piasecki/Vertol/Boeing that went back to the Piasecki PV-3 of 1945.

http://www.aviastar.org/helicopters_eng/boeing.html

Note some of the more interesting Chinook and other derivatives that never made service, including the giant CH-62!

So the question is really, was the Bristol Type 173 influenced by the Piasecki designs?

Edit: Pagen posted whilst I was looking up the link!