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By contrast, North Korea has defied all international sanctions to build up a formidable arsenal of nuclear warheads and intercontinental ballistic missiles, enough to make any potential attacker think twice.

He has more nuclear warheads, his weapons are more advanced, and the sanctions that were supposed to put pressure on his regime have all but collapsed, thanks largely to Vladimir Putin.

Meanwhile, China is a "sophisticated and persistent challenge", the review warns, and is "likely to continue seeking advantage through espionage and cyber attacks" and is expected to have 1,000 nuclear warheads by 2030.

The prime minister is also expected to confirm the UK will spend £15bn on its nuclear warhead programme.

Early this year it claimed it fired a new intermediate-range ballistic missile tipped with a hypersonic warhead which it said "will reliably contain any rivals in the Pacific region".