Work to deliver Britain's Trident nuclear deterrent at the BAE Systems facility in Barrow has emerged as the least delayed and least expensive when it comes to overspend.

As previously reported by in-Cumbria, Whitehall spending watchdog The National Audit Office (NAO) issued a warning that the Ministry of Defence programme was, so far, £1.3 billion over its initial budget.

It highlighted poor management of the infrastructure to build and maintain the country’s newest Dreadnaught class of nuclear submarines was to blame for the eye-watering overspend and overruns.

However, Barrow has emerged as the least problematic of the three sites involved in the project.

Work is being carried out on two buildings – the first currently nearing completion and the second just starting – in preparation of building the Dreadnaught class submarines.

Also involved is the Atomic Weapons Establishment site at Burghfield, West Berkshire, where a new nuclear warhead assembly and disassembly facility is being created, and the Rolls Royce site at Raynesway, Derby, where facilities are being built to design and produce the the nuclear reactor cores that will power the Barrow-built submarines.

While the anticipated delay for the project in Barrow stands at 1.7 years, work at Raynesway is 5.1 years behind schedule and Burghfield 6.3 years.

Meanwhile, the overspend at Barrow is estimated to be £240 million, almost half the £474m figure for Raynesway, and well below the figure for Burghfield, which is £1.8bn and represents a 146 per cent increase from the original £734m forecast when work started in 2011.

While the overspend in Barrow is less than the rest it is 116 per cent rise higher than the original budget of £111m when work started in 2016. The project is forecasted to be complete in 2022.

In its report the NAO accused the Ministry of Defence (MoD) of failing to learn from past mistakes in delivering the Defence Nuclear Enterprise to replace ageing facilities, some of which date back to the 1950s.

It said "inappropriate" contracts with outside contractors and beginning building work on facilities before the designs were "sufficiently mature" had added hundreds of millions of pounds to costs.

And it also highlighted a lack of technical skills within the MoD which resulted in the "gold-plating" of designs as staff were unable to challenge regulators when they insisted upon overly complex specifications.

The findings come as the Prime Minister's chief adviser Dominic Cummings is preparing to launch a far-reaching review of defence spending amid long-standing concerns that billions are being squandered on botched procurements.