It's the issue of our times - and three Cumbrians are playing a key part in the legal firm at the heart of Brexit.

Lawyers Sally Britton and Michael Armstrong - former pupils at Trinity School in Carlisle - are partners at London-based Mishcon de Reya.

Their firm represented businesswoman and campaigner Gina Miller in the landmark constitutional law challenge about how Article 50, the process by which Britain leaves the European Union, is triggered.

Mrs Miller was the lead claimant in the historic legal action.

She argued that individual members of the Cabinet had no legal power to trigger Article 50 without the prior authorisation of parliament and MPs.

But at the centre of the firm involved are two people who grew up just a short distance away from each other in the north of Carlisle.

Sally left Trinity School in 1992 and studied law at Manchester University.

Prior to qualifying as a lawyer she worked in brand management for companies like Heinz and Budweiser.

She used to live on Brampton Road in Stanwix, just a few streets from fellow Mishcon de Reya partner, Michael, who lived on Millcroft, off Longlands Road.

She said: "It is a funny coincidence that Michael and I grew up streets apart yet ended up working for the same law firm in London."

Their colleague Lisa Tremble - who went to Stainburn School in Workington - was also heavily involved in the case.

Sally, 42, said: "It is one of the most high profile political issues facing this country. This was a big case for my firm."

She added she was proud to work for Mischcon, particularly as it took on work linked to such a major issue.

Sally also paid tribute to the work of her colleague Lisa, adding: "She has been great throughout this case. She is very involved in what she does."

Lisa said: "I worked closely with Gina and our lawyers to provide strategic advice, which has included managing the unprecedented global media interest in the case.

"It is certainly one of the most high profile and historical cases Mishcon de Reya has ever worked on.

"At the centre of this case was the rule of law, the separation of powers and the independence of the judiciary."

The firm says their case successfully argued that as a matter of UK constitutional law the Government did not have power under the Royal Prerogative to give notice to withdraw under Article 50 of the Treaty on European Union.

Lisa, 42, added: "The Supreme Court agreed with our client's case that under the UK's constitution, Parliament is sovereign and only Parliament can make or unmake laws and therefore ruled that legislation would be necessary.

"As a result the government published The European Union Notification of Withdrawal Bill to gain parliament's permission to start the Brexit process."

Formal negotiations can begin once the UK has given notice of Brexit under Article 50 of the Lisbon Treaty, which Prime Minister Theresa May has promised to do by the end of March.

Last week MPs voted to allow the prime minister to do this as they backed the European Union Bill by 498 votes to 114.

MPs discussed the bill in more detail this week when it reached the committee stage in the Commons.

Sally's parents, retired doctors John and Nancy Britton, still live on Brampton Road.