Defence row exposes tensions over how to keep UK safe

Defending the realm is supposed to be a prime minister's first priority. Yet Sir Keir Starmer is accused by two departing defence ministers of failing to provide the means to meet that vital aim.

So who is right? Is the government not doing enough to keep us safe? Or is this merely a Whitehall spending row that has gone catastrophically wrong?

The government currently allocates about £66bn for defence. That supports the UK's armed forces which remain highly regarded by friend and foe alike.

The money also pays for the nuclear deterrent. The UK is surrounded by water and has strong allies. All of these factors contribute to keeping us safe.

But successive governments have struggled to get a grip on defence spending. They spent less after the Cold War ended and failed to spend more as the world became more dangerous. As a result, the army, navy and air force contracted.

To its many critics, the Ministry of Defence failed to spend well what money it got, botching procurement after procurement, delivering new equipment late and over budget. Whitehall often failed to resolve its internal tensions, both No 10 and Cabinet Office unable - or too weak - to manage repeated rows between Treasury and MoD.

What is different about this row is its context. The world is changing fast. The nature of the threat against the UK is changing. Less immediate concern about non-state actors and militant groups such as al-Qaeda or ISIS. More focus instead on state-on-state aggression such as from Russia and Iran.

That threat is increasing. In his letter replying to John Healey's resignation, the prime minister wrote: "The world today is more dangerous and uncertain than at any point in our lifetimes".