BORIS Johnson’s plan for a bridge from Scotland to Northern Ireland may have been cancelled to little surprise or regret. But a more important, realistic bridging role for Britain has taken two potentially fatal hits in the past month as well.

The notion of the UK as a bridge between Europe and the US for defence and diplomacy has been central to how post-war Britain has seen its global role, especially after we joined the EU. After Brexit, defence and security were presented as the areas of closest continuing cooperation with our former EU partners. In recent months a particular cooperation with France has been highlighted.

The bridge’s two piers, on the European side and on the American, have looked wobbly in the last few years. But the gulf which the bridge has to span has now suddenly widened in unexpected ways.

The abruptness of the US departure from Afghanistan, and the minimal, if any, notice to British, German and French allies showed that the apparent return of more predictable foreign policy under President Biden hadn’t narrowed the Atlantic as much as many hoped. For the UK, that was a deep, but external, shock.

The effects of the newly announced “AUKUS”, a triangular arrangement between the US, Australia and Britain, are not yet fully apparent but any damage is more self-inflicted. And there has been damage. AUKUS’ main feature so far, supplying British and American technology and perhaps construction work for Australia’s first nuclear-powered submarines, has seriously rocked Britain’s relationship, and especially our hitherto valued defence relationship, with France.

The French Government was told suddenly, on the day AUKUS was proclaimed, that its €56 billion deal (£56bn) signed in 2016, to provide conventionally-powered submarines for the Royal Australian Navy, was revoked. The hurt to France goes deeper than the significant commercial loss. In June Scott Morrison, Australia’s Prime Minister, visited Paris, when the submarine deal was hailed as “a pillar of partnership and a relationship of trust which will bind us for decades to come”. In August, the French and Australian Defence Ministers met, declaring their wish to “deepen their cooperation in the domain of industry and defence”, underlining the “importance of the future submarine programme”.

It is odd for the US to trash so lightly one of their two main European NATO military partners, especially the one with by far the biggest military commitments in the Indian and Pacific Oceans: 7,000 troops, 7 naval ships and aircraft permanently based east of Suez, and 500,000 citizens in Pacific territories.

For Britain, the benefits – not nothing, with reassured job prospects for hard-pressed Barrow-in-Furness – must be set against the further shaking of French trust in Britain. This will unavoidably affect expanding UK/French defence co-operation. But it cannot be isolated from the growing uncertainties surrounding British trustworthiness in its international commitments more generally, where France helps steer the wider EU – and others will have noted our involvement in this transaction too. I would like to think this had been carefully thought through and weighed. But I wonder.

George Fergusson was Secretary of the Defence *& Overseas Committee in the UK Cabinet Secretariat, 2003-06