Manning led a team of designers to produce a coastal patrol and anti-submarine flying boat to meet Air Ministry Specification 23/23.

In January 1923 the Air Ministry contracted English Electric to build a prototype and the new design was built at Preston, then moved by road to Lytham for flight trials.

[2] While being towed by the tug the strong current struck the pier and it had to be beached again, it was recovered to the company slipway the following day.

[2] The first Kingston I N9709 was ready a few months later, only small changes were made from the prototype including a slightly larger beam and two-bladed propellers.

[2] The flying-boat was delivered by rail to the Marine Aircraft Experimental Establishment at Felixstowe in November 1924 for acceptance trials.

[2] On 25 May 1925, just after becoming airborne the engines left their mountings and the wing structure failed causing cracks in the hull, the aircraft floated and the crew escaped without injury.