The Vanguard was brought into revenue service on 17 December 1960, around the same time as the commercial availability of a new generation of jet-powered airliners; as a result, these competitors quickly overshadowed its performance and led to the type being largely ignored by the market.

This envisioned successor airliner would possess economics 10 per cent greater[clarification needed] than those of the Viscount, while also being considerably faster throughout all operational stages.

[1] Out of BEA's internal analysis of various options, which studied both turboprop and pure jet propulsion arrangements, it became clear that a larger aircraft that could accommodate bigger payloads was highly desirable.

[2] It was around this time that Vickers' design team also discarded notions of adopting a swept wing, largely due to its providing little benefit at the envisioned airliner's 350-knot (400 mph; 640 km/h) cruise speed, as well as its inferior performance during the approach stage of flight.

Furthermore, TCA wanted a low-mounted wing, which would make the aircraft easier to refuel, de-ice and service, as well as giving a statistically significant improvement in survival in the event of a water landing.

This conceptual aircraft, referred to as the Type 870 Scheme 16a, could accommodate 88 passengers, a cruising speed of 360 knots (420 mph; 680 km/h) at 25,000 ft (7,600 m), and payload of 20,000 lb (9,100 kg).

[5] Following some relatively minor revisions, which largely bolstered the gross weight upwards, that were made to better suit the design to the needs of global customers, the definitive Type 950 proposal emerged.

[6] At the time, TCA was, while intensely interested in the airliner, not yet willing to commit itself, partially due to the basic model not entirely fulfilling its requirements, such as the level of capacity for air mail.

[6] Vickers recognised that a high-density seating configuration, accommodating up to 139 passengers to be carried, would likely be attractive to more operators, and designed the Type 952 model for this market.

As the Vanguard's production line was coming online at Vickers' Weybridge facility, BEA recognised that, due to the typically short length of its routes, a higher density economy seating configuration could be adopted without impacting performance.

[10] While development proceeded relatively smoothly, apart from over 2,000 flights being required to resolve unacceptable stalling characteristics, the last weeks of trials with BEA in early 1960 uncovered some engine-related difficulties, necessitating a brief delay while the compressor rotor was modified.

[13] Passengers typically preferred the additional speed, even at the disadvantage of greater operating costs and thus higher ticket prices, that came with jet-powered airliners.

In spite of this arrangement, according to Andrews, the onboard electrical systems were a major advance over the previous generation of airliners; amongst other capabilities, the engines could be started without the aid of a ground support cart.

[17] The Vanguard possessed relatively docile stall characteristics, in part due to the dihedral positioning of its horizontal stabiliser, which kept it clear of the jet efflux from the engines and aided longitudinal stability.

On flights up to 300 miles (480 km), such as from London to Paris, Brussels and Amsterdam, the type could match the block times of the pure jets which were being introduced in the early 1960s.

[24] BEA operated nine Vanguards modified to the V953C "Merchantman" all-cargo layout from 1969, with the first two conversions being designed and carried out by Aviation Traders Engineering Ltd (ATEL) at Southend Airport.