That sketch of the HS.134 caused me to dig out Graziano Freschi's excellent book "The BAC Three-Eleven". The following is his description:
"The HS134 study was launched in 1966 on the basis of a radical development of the Trident airliner...to be powered by two RB178 high bypass turbofans mounted on pylons under the wing. The later was based on a high aspect ratio, highly efficient supercritical design. The Trident cockpit and fuselage width were retained, but the stretched fuselage and low tailplane mounted at the end of the fuselage gave the aircraft the general appearance of the much later Boeing 757....The only good that came out of Hawker Siddeley's effort on the HS134 was the know-how on advanced supercritical aerofoils and on the general aircraft configuration (large wing mounted engines), knowledge that the company later put to good use in helping with design of the Airbus A.300"
So HS pretty much defined the configuration of the modern under-wing turbofan twin, both narrow and widebody