The defence of the realm is the primary duty of any prime minister and, so far as this particular legacy is concerned, David Cameron may be tempted to congratulate himself on a job well done as he exits Downing Street.

During six years of premiership, Cameron has scaled back Britain’s military involvement in overseas conflicts to the point where we no longer witness the bodies of soldiers being paraded through the streets, as was often the case in the Wiltshire town of Royal Wootton Bassett when the Afghan campaign was at its height. Nor, despite the heightened level of the security threat, have the British Isles suffered another major terrorist attack on the scale of the July 7 attacks on London in 2005.

The murder of Fusilier Lee Rigby in 2013 by two extremist terrorists certainly showed that radicalised young fanatics have lost none of their desire to bring terror to British streets. But the increased sophistication of the intelligence and security services in tracking potential suspects meant that the most likely target of a major attack, the London Olympics, passed without incident.

And yet, while it is true that Cameron has succeeded in limiting the exposure of the British public to the harsh reality of combating terrorism, he cannot claim to have made the world a safer place. On the contrary, it could be argued that Cameron’s policy of limiting Britain’s involvement in overseas conflicts to the bare minimum has made the global security picture much worse. Moreover, his insistence of wasting billions of pounds on foreign aid while making drastic cuts to the defence budget means that the country may struggle to defend itself should any new challenges arise.

For, make no mistake, on Cameron’s watch, Britain has suffered a dramatic decline in its standing as a global power. Officials in Whitehall and the world’s major capitals now freely accept that Britain’s ability to project itself on the international stage has been “hollowed out”.

The rot set in with the 2010 Strategic Defence and Security Review, when Cameron and George Osborne argued that drastic cuts to the defence budget were necessary to help the government achieve its objective of balancing the books. In fact I’ve always believed the cuts were implemented to help them achieve their goal of making sure Britain did not involve itself in any more unpopular wars on the scale of Iraq and Afghanistan.

If Britain did not have enough soldiers, sailors and airmen, then it could not participate. Thus when, the following year, Cameron decided to lead the campaign to overthrow Libyan dictator Colonel Muammar Gaddafi, he did so by applying the minimum military input, relying on air strikes and special forces to complete the job rather than deploying conventional ground forces. The same, risk-averse template has been used to tackle the threat posed by extremists in Iraq and Syria, the only problem being that, in the absence of a credible ground force, it is difficult to bring hostilities to a satisfactory and lasting conclusion.

When Cameron entered Downing Street, Britain only had to contend with the ongoing conflicts in Iraq and Afghanistan. Now Britain faces threats on multiple fronts from countries like Libya, Syria, and Iraq, while the conflict in Afghanistan, where Cameron oversaw the withdrawal of British forces 18 months ago, shows every sign of returning to full-scale civil war.

Cameron is not the only one to blame for this worrying escalation in the global threat. United States President Barack Obama’s refusal to provide the western alliance with firm and effective leadership has also played its part, but the unwillingness of major powers like Britain to get their hands dirty in resolving conflicts has lent encouragement to those who seek to exploit western weakness for their own ends. It was surely no coincidence that Russian President Vladimir Putin decided to invade Ukraine shortly after Cameron failed to win parliamentary backing for his ill-considered plan to launch air strikes against the Bashar Al Assad regime.

Thankfully, the pendulum already appears to be swinging back to a more robust approach to defending British interests. In one of his last acts as prime minister, Cameron this week signed a £3 billion (Dh14.6 billion) order for Boeing to provide a new fleet of maritime patrol aircraft, which are deemed vital to protecting the Trident nuclear deterrent — whose renewal parliament will vote on next week. Cameron also used last week’s Nato summit to announce the deployment of hundreds of British troops to eastern Europe — a clear signal that, despite Brexit, Britain remains fully committed to the alliance.

None of these issues are Cameron’s responsibility now, but when it comes to assessing his legacy, the multitude of problems he is bequeathing to his successor suggests his risk-averse approach ultimately did more harm than good.

— The Telegraph Group Limited, London, 2016

Con Coughlin is the Telegraph’s defence editor and chief foreign affairs columnist.