Development of the turret began in 1943 as part of a program to improve the Lancaster's defensive armament but it did not enter production until late 1944.

The Royal Air Force (RAF) ordered 600 Rose turrets in June 1944 and 400 were completed by the end of the Second World War in Europe.

The turret was generally regarded as an improvement over previous designs, although its guns had a high rate of stoppage during combat.

At the conclusion of the conference, Air Vice Marshal Ralph Sorley, who was responsible for the RAF's technical requirements, stated that "every effort should be made to introduce the mid-upper and redesigned tail turrets in a year's time" and that the Lancaster's armament would be obsolete if this deadline was not met.

Harris became frustrated with the slow progress of the project and did not believe that the Air Ministry would be able to produce the turret in time.

As a result, he decided to go outside the official channels and personally asked the small Gainsborough firm of Rose Brothers to develop a turret for the Lancaster; this company had previously developed an improved gun mounting for the Handley Page Hampden medium bomber in 1940 upon a request from Harris.

[10] The Rose turret was a roomy design equipped with two .50 in (12.7 mm) Browning AN/M2 heavy machine guns.

The considerable internal space meant that the turret could be fitted with two seats: a layout in which one man operated the guns and the other fed targeting data into the gunsight computer was developed, but not used in practice.

Previous designs had perspex around the gun position, but in the Rose turret there was no protective shielding immediately in front of the gunner.