AN independent Scotland could succeed in staying in the European Union, a leading constitutional expert has argued.

Jeff King, a professor of law at University College London, and a specialist in the UK constitution said the move could be “a sweet deal” for the remaining 27 states.

Independence for Scotland could very well be a sweet deal for the rest of the European Union,” he told a European Parliament event.

“The independence movement, which has some extremely good politicians in it, is going to be in the strongest position they have been for a long time.”

His comments, reported in the New Statesman, come after arguments over Scotland’s possible status post-Brexit were played out on both sides of the English channel.

Ahead of an appearance at a Holyrood committee today David Mundell yesterday claimed there were “no circumstances” in which Scotland could remain in the EU when the UK leaves.

But earlier this week German MEP Elmar Brok, an ally of Chancellor Angela Merkel, said the EU27 could “make a fuss” over Scotland in the Brexit negotiations to gain leverage over the UK during the Article 50 talks, suggesting EU leaders were prepared to smooth the way for an independent Scotland to join the bloc if relations with the UK Government break down.

Meanwhile, Jean-Claude Juncker yesterday warned the UK can expect a hefty bill for leaving the EU and could have to wait years for any new trade relationship to be established with the bloc.

The European Commission president said Britain will have to pay the bill and agree withdrawal terms before it can embark on any new discussions about the future.

Estimates suggest the demand presented to Theresa May when she launches the Article 50 negotiations may be as high as €60 billion (£51bn) over the next six years, covering the UK’s share of the cost of programmes which it signed up to as part of the 28-nation bloc, as well as pensions for EU officials who served during its 45-year membership Juncker used a French slang term to tell the Belgian Federal Parliament in Brussels yesterday he expected the bill to be very “salty” – meaning hefty or pricey.

“Our British friends need to know – and they know it already – that it will not be cut-price or zero-cost,” said the Commission president. “The British will have to respect the commitments which they played a part in agreeing.

“Therefore the bill will be – to use a rather vulgar term – very salty. It will be necessary for the British to respect commitments which they freely entered into.”

Juncker stuck to Brussels’ position that withdrawal arrangements – including the “exit bill” – must be agreed before moving on to potentially lengthy negotiations over future trade relations.

The UK Government insists these talks can run in parallel after May kicks off negotiations under Article 50 of the EU treaties – something she has promised to do by the end of March.

But the Commission President told Belgian parliamentarians: “This will be a difficult negotiation, which will take two years to reach agreement on the exit arrangements. To agree on the future architecture of the relations between the UK and EU, it will need years.”

He restated the Commission’s position there will be no membership of the European single market for the UK unless it signs up to freedom of movement for workers.

Mundell will today be quizzed by MSPs on a Holyrood’s committee.

“I think it is important to be clear, because there has been a lot of public debate on this point – that Scotland will not be in the EU at the end of this process,” he will say in his opening statement. “There is no set of circumstances in which Scotland could remain a member of the EU after the rest of the UK has left. If Scotland’s constitutional position were ever to change, it would have to apply to be a member of the EU afresh – and we should not make easy assumptions about the length of time this would take, the process Scotland would have to follow or the terms of membership that may be on offer.”

Mundell’s comments were dismissed by Alyn Smith, the SNP MEP, who said: “I can see why Mr Mundell would try to say things are impossible and we should put ourselves at the mercy of Theresa May’s negotiations but I am not willing to be told to sit quietly by a Tory Government rejected by the people of Scotland.”