ST Kitts and Nevis in the Caribbean seems far from Scotland’s current political debate. But if Nicola Sturgeon doesn’t get approval from the Supreme Court in the case which started this week for the independence referendum she wants, the islands’ path to independence – by electoral mandate rather than referendum – may become an unlikely precedent for her fall-back position. Electoral mandates were how most British territories became independent during decolonisation.

Since the 1990s referendums on independence, not election results, have become the norm. Examples have been Bermuda (in 1995), Northern Ireland (1998), Gibraltar (2002), Falkland Islands (2013) and Scotland (2014). The majority, each time, voted to maintain the status quo.

These referendums, and Anguilla and Barbuda’s decision by electoral mandate, all had quirks relevant to the debate in Scotland.

Bermuda’s independence referendum was organised by the Bermuda Government, but with the British Government’s blessing. With an Opposition boycott – perhaps like that which some Scottish unionists have contemplated for an Indyref2 – there was nonetheless a majority turnout – just, at 56%. Seventy-five per cent voted against independence.

Northern Ireland’s 1998 vote endorsed the Good Friday Agreement, including agreement to a future referendum if the Secretary of State believes “that a majority of those voting” favour leaving the UK and joining a united Ireland. In both the 1998 referendum and the potential future poll, 50% plus one was declared enough to carry the decision, whatever the turnout.

In Gibraltar the British link was affirmed by a referendum approved by the UK Government in 1967. But in 2002 the Gibraltar Government organised another poll, against British ministers’ wishes, who refused to recognise its result. This poll pre-empted the joint sovereignty which the UK was discussing Spain. It came down strongly against the idea.

The Falkland Islands referendum asked whether the UK link should be preserved. If the vote had been No, a second vote would have settled new arrangements. (This parallels the two-stage Brexit vote once envisaged by Eurosceptics, including Jacob Rees-Mogg: he argued in Parliament in 2011 for a Brexit referendum, followed by another on the negotiated arrangements, later opposing this).

Even St Kitts/Nevis’ precedent of gaining independence by mandated parliamentary majority referred to a referendum. Nevis, reluctantly federated, won the right to claim independence from St Kitts, if it wanted, by a two-thirds referendum majority. It exercised this right in 1998 – but the independence-seekers got only 62% and the proposition failed.

So, although there are precedents for going independent by electoral mandate, they are now distant. The issue, at least for Overseas Territories, was examined by the Commons Foreign Affairs Committee in 2007. Meg Munn, then Overseas Territories Minister, said a referendum was the British Government’s preference. But it might sometimes be acceptable if a party won a “clear” majority on a manifesto commitment for independence. She offered the hypothetical case of a party committed to independence and winning 90 per cent of the vote. The clear risk is that other issues can cloud – or be claimed to cloud - an electoral mandate.

George Fergusson is a retired senior diplomat