In a bid to appease the Tory right, Conservative leaders have for years flirted with taking the nuclear option of leaving the European Convention on Human Rights.

Jet fuel will be poured onto that row on Wednesday if the Supreme Court upholds a ruling that Rishi Sunak’s Rwanda asylum scheme is unlawful as a vengeful Suella Braverman waits in the wings.

Suella Braverman visit to Greece
Suella Braverman will be on the attack over the ECHR (Stefan Rousseau/PA)

– What is the ECHR?

After the darkest days of the Second World War, political leaders including Winston Churchill advocated for a Council of Europe (CoE) to oversee a charter of human rights.

This led to the European Convention on Human Rights (ECHR) being signed in 1950. Its drafting was led by Conservative MP Sir David Maxwell-Fyfe and the UK was among the first to ratify the international treaty.

Today the legal commitment signs up all 46 CoE members to abide by rules on rights to life, liberty and expression, and protection from torture, degrading treatment and slavery.

It is not linked to the European Union, so Brexit did not affect the UK’s obligations.

The European Court of Human Rights, in Strasbourg, makes binding judgments on the convention.

– Why is the convention back in the headlines?

The Supreme Court will hand down its judgment on Wednesday on whether the Prime Minister’s plans to remove asylum seekers who arrive on small boats to Rwanda. It is central to his pledge to “stop the boats” crossing the English Channel.

The Government went to the highest court in the UK after appeal judges found the policy was unlawful because the east African nation was deemed unsafe. The ruling also touched on the ECHR.

If he loses the appeal, Mr Sunak may consider whether there is any scope to take the case to Strasbourg.

In a scathing attack on the Prime Minister after her sacking as home secretary, Suella Braverman said his legislation is “vulnerable to being thwarted yet again” in Strasbourg even if it wins in the British legal system.

– Does Rishi Sunak’s Government want to quit the convention?

The Prime Minister promised to do “whatever it takes” to stop small boats but has been resisting taking action on the ECHR, other than to argue for reform over the order that blocked the inaugural flight to Kigali last year.

The most strident rhetoric came from Mrs Braverman, repeatedly signalling she wanted to quit the “politicised court”.

Even after she was sacked by Mr Sunak, immigration minister Robert Jenrick said they must halt the boat crossings “no ifs, no buts” in an interview with the Telegraph.

But in the past, James Cleverly – who has inherited the Home Office from Mrs Braverman – has taken a more moderate approach.

In April, while foreign secretary, he said he was “not convinced” leaving the ECHR was necessary to have a robust immigration system.

He said the European countries that are not signatories are a “small club”, telling the Guardian: “I am not convinced it is a club we want to be part of.”

Mrs Braverman may want to exact revenge for her sacking while trying to boost her popularity on the right of the party, in the event of a leadership contest, by calling for Mr Sunak to quit the convention.

– Which European nations aren’t signatories?

Modern warfare
Vladimir Putin’s Russia is an outlier in not being part of the convention (Nick Potts/PA)

The outliers in Europe that are not signed up to the ECHR are a conspicuous duo: Vladimir Putin’s Russia and Belarus.

Back in the 1960s, Greece left the convention after a military coup abolished democracy.

– Have the Tories always wanted to leave?

When he was prime minister, Lord David Cameron said he ruled out “absolutely nothing” in a bid to scrap Labour’s Human Rights Act, which incorporated the convention into British law.

Frustrated by Strasbourg’s rulings while home secretary, Theresa May urged people not to vote to leave the EU but instead focus on the ECHR.

Both Boris Johnson and Liz Truss also kept the threat on the table as they sought to placate the right of the party.

But the Conservatives are far from united over the issue, with more moderate MPs standing strongly in support of the UK’s international commitments.