A former chief of the SAS has backed the campaign for a second Brexit referendum and warned that a no-deal outcome would lead to major security concerns for the UK.

It is essential, Major General Jonathan Shaw told The Independent, to allow voters a choice, now that the reality of leaving is becoming clear, stressing that crashing out of the European Union without an agreement would lead to serious risks “on matters like intelligence sharing, on terrorism, on hybrid warfare and cyber threats.”

Major General Shaw views the 2016 referendum result as Britain’s “Arab Spring moment” in which popular resentment on a number of issues and a desire for change coalesced around a “no” vote, without any clear idea of its long-term consequences.

“It was a protest vote about all kinds of things including the EU – it was an emotional vote for many.

“It was also a vote for the negative, and the problem with something negative like that is difficult to make something constructive out of it,” Major General Shaw said.

“It was, if you like, a sort of Britain’s Arab Spring moment, a protest where the ultimate outcome was not known. The people of the United Kingdom should be allowed to make up their minds, either way, when the full detail of what is actually involved in Brexit does become known.”

Major General Shaw, who was director special forces, the commander of British forces in Iraq and assistant chief of defence staff during his military career, had, at one stage, considered voting to leave the European Union, but changed his mind after analysing the options.

“I could understand the dissatisfaction with the democratic deficit in the EU and the plan for an “ever closer union”. One can oppose these. But there are, for me, other things to consider, including security, in which I believe it is better to be in the EU.”

“We now have more information. People can analyse that when it comes to a new vote, they can change their minds or stay as they were.”

The idea of a second referendum would probably have been fanciful a while ago, but now there seems to be an impetus behind it Major General Jonathan Shaw

There could be apprehension, said Major General Shaw, that an immediate referendum would complicate negotiations for the British government and tempt Brussels to take a tougher stance.

“But a vote when the final details are available, after the talks have been concluded, will allow people to make up their mind on whether they are better off as they are, or want the changes being proposed” he held.

“The idea of a second referendum would probably have been fanciful a while ago, but now there seems to be an impetus behind it – a view that these are such fundamental issues that all options must be carefully considered.”

A no-deal outcome would, Major General Shaw points out, lead to extremely serious problems on the security field.

“There would be major concerns on matters like intelligence sharing, on terrorism, hybrid warfare cyber threats, this new field of conflict, especially now that we have state actors involved in this, we need the help of other member states in this, and, they of course, need ours,” he said.

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“It is theoretically possible to have a separate security agreement, but there are a whole host of issues there including data protection, European laws and UK laws.

“On the purely military side, Nato, of course will continue, and the UK’s role in it will not be affected by Brexit.

“But one has to take the Trump factor into account, other member states are now unsure on how much Europe can depend on US under his administration and this is something which should be of concern to the UK as well. One cannot tell what Mr Trump may, or may not, do, but it is a factor to consider”.

There is yet to be a breakthrough on post-Brexit security cooperation between the UK and the European Union – a matter seen as one of utmost importance. Although Theresa May has insisted that the UK wants a wide agreement on the issue, there has been no substantial progress in the talks being held.