The English Democrats chairman is expecting his case to be heard in the High Court within five to six weeks. His legal argument focuses on Theresa May not having the legal power to delay Brexit past the original deadline of March 29. Mr Tilbrook has argued although the under-pressure Prime Minister had the power to begin Britain’s two-year withdrawal process from the European Union, she in fact did not have the power to amend it. The Brexiteer claims this means the extension granted by Brussels last month until October 31 is null and invalid, and Britain actually left the EU on March 29.
Speaking to Express.co.uk, Mr Tilbrook said: “We have a very strong legal argument – I’m 80-90 percent confident we will be successful.
“Government lawyers have tried to rubbish our case, but I’ve not had any legal professional tell me we haven’t got an excellent chance of succeeding.
“Theresa May and her Government had no right to agree an extension to Brexit.
“We should have left the EU as proposed on March 29, and if we win this case, we will finally be out of the bloc.”
Commenting on the specifics of the case, Mr Tilbrook added: “The notice was served and expired, so it means you are out.
“The Government served their notice under that Act of Parliament and if you look at the Act in question, it’s extremely short at 137 words.
“That only states the Prime Minister only had the power to serve notice to withdraw the UK from the EU, and nothing else.”
But Government lawyers have since hit back, claiming Mr Tilbrook’s case is “totally without merit”.
They argue the 2017 Act of Parliament in question that allows Mrs May to trigger Article 50 did not set a date for Britain to leave the EU.
This, they add, did not restrict the Government’s power to change the date.
They lawyers said: “If the claimant is right, the UK would have withdrawn from the EU by accident.
“That would be directly contrary to the evident intention and belief of Parliament and the other member states of the EU.
“That would be a startling legal position indeed.
“Parliament has acted on the basis of those lawful extensions and given effect to the extension of the withdrawal date.”
Mr Tilbrook’s upcoming legal challenge is similar to Gina Miller’s high-profile court battle against the Government in 2016, when she challenged its authority to implement Brexit without approval from Parliament.
Both the High Court and Supreme Court found in her favour, forcing MPs to vote on the former start of the Brexit process.