The highest-security fences surrounding Britain’s military bases can be broken into within five minutes, Royal Air Force insiders have claimed.

Spending “many millions” to install barbed wire-topped high fences at every base would therefore not materially improve security, they argued.

Just weeks after Palestine Action activists broke into RAF Brize Norton, Britain’s largest air base, the soon-to-be proscribed group has pledged to raid others in protest against Israel’s war in Gaza.

The Telegraph has found a number of the RAF’s most important bases are susceptible to such attacks, with “vulnerable” airstrips protected by hedges, wooden fences or nothing at all.

Security weaknesses included wooden fences, drystone walls, weakly defended emergency access points and unmanned gate barriers.

A mooted future home for the new nuclear-capable F35 fighter jets is kept behind a 5ft-high fence.