Why Britain persisted with the Avro Shackleton

Why did Britain persist with the Avro Shackleton despite its deficiencies?

Because it remained a reliable design that British planners believed could still be developed further.

The premise overstates the Avro Shackleton's deficiencies. The aircraft had shortcomings, but it was also a reliable design that British decision-makers believed they could develop further. Persistence with the established platform reflected confidence in its reliability and growth potential, without assuming that it was flawless.