A war book first conceived over a hundred years ago could be revived to prepare the nation for possible war, the head of the armed forces has said.

The top secret manual produced in the First World War became the first of many so-called detailed ‘government war books’.

It was produced right up until the early 2000s when it was mothballed in a cost-cutting exercise.

Now Air Chief Marshal Sir Richard Knighton said the book could be resurrected to help prepare the public for war.

It would draw on lessons from the Cold War but ‘in a modern context, with a modern society, with modern infrastructure’, he said.

Led by the Cabinet Office and involving all other government departments, the book detailed procedures which were regularly rehearsed and is believed to have boosted national resilience.

A 1976 copy of the book revealed a fascinating, physical manuscript of hand-typed and string bound pages.

It contained detailed lists and plans about how to mobilise the military as well as civilians and industry and crisis plans including ones for shutting schools, clearing hospitals, rationing food and even storing national treasures.

‘NATO describes the transition to conflict as a military component, but it also has a civilian component,’ the defence chief said.

He said civilians now needed to be aware of increasing threats to the relative peace the UK has enjoyed for over 30 years.

‘That requires us to educate ourselves and help the population understand some of those threats and help them understand what they can do to support the nation and potentially support the armed forces,' he added.

He explained: ‘I talked before Christmas of the need for - when we think about renewing our water infrastructure or electricity or transport infrastructure – thinking about the threat of action from an adversary that is above the threshold of war, not just a hybrid threat.

‘And think about how we build in that resilience as we renew it and that requires making some different choices and different priorities and that work that the Cabinet Office is doing across the whole of government is something that I really welcome.’

Speaking at the London Defence Conference yesterday, he also talked about the challenges in defence spending if the military was working towards a war footing.

Opposition politicians say the delay to detailed defence spending plans which should have been published by the government following its Strategic Defence Review last autumn has left the country ill-prepared to defend itself as well as leaving the UK defence industry in limbo.

Conservative leader Kemi Badenoch said earlier today that it was ‘a national scandal’ that the spending plans were still on hold and accused the government which has promised a boost in defence spending to 3.5% of GDP of ‘prioritising bullets over benefits’.

Air Chief Marshal Knighton said: ‘What I want is a defence investment plan that is properly funded and delivers what we want.

‘If that takes a bit longer, I'd rather have something that works and we can deliver.’

The chief of the defence staff also said the UK ‘was ready’ to take on threats from Russia’s ‘shadow fleet’ even though ships already spotted off the coast have not been apprehended.

Questioned about whether ships could be boarded, he said the knowledge that we were ready to target a sanctioned tanker was already leading Moscow to divert them, commenting bullishly:

‘Be in no doubt. We are ready.’

But speaking at the conference today, Ms Badenoch said Britain was not prepared for conflict and dismissed Defence Secretary John Healey’s comments yesterday that we are ready to defend ourselves.

‘I am not here to lie to you. We are not ready. At a time of war in Europe and a time of war in the Middle East and at a time when these conflicts are affecting every family across Britain, at a time when Britain’s place in the world is in flux, our government literally does not have a plan.

‘There is no plan for how the government is going to buy equipment, weapons and munitions. There is no plan for how to enact the Strategic Defence Review. There is no plan for re-arming Britain. I asked Keir Starmer about this at Prime Minister’s Questions and he put his head in his hands.

‘The reason there is no plan is because they have no idea how they are going to pay for it so it is time to make some tough choices. The question is not whether Britain should re-arm but it is what choices we must make to do so.’