The W.8 (also known as the H.P.18) was the company's first purpose-built civil airliner although it was a development of the wartime Handley Page Type O/400 bomber via the O/7, O/10 and O/11 transports.

It had an enclosed cabin for (in most versions) 12 passengers, along with two crew in an open cockpit, and has the distinction of being the world's first airliner to be designed with an on-board lavatory.

To meet an Air Ministry ruling, the capacity was reduced to 12 passengers and the fuel tanks were moved from the engine nacelles to above the top wing.

In 1921 the Air Ministry ordered three aircraft, built as the W.8b, for use by Handley Page Transport, and later by Imperial Airways, on services to Paris and Brussels.

Planned but unbuilt 1923 alteration of W.8b for 1923 with the same engines but seating 16 passengers in a cabin lengthened by removal of the radio compartment and a reduction of freight capacity.