Sharia, or Muslim religious law, has been highly controversial in the UK. Interpretations of Sharia are associated in other countries with harsh penalties unknown in the UK; campaigners and politicians worry that Muslim women are discriminated against when family disputes are resolved under Sharia.
Are there 'Sharia courts' in Britain?
While there are undoubtedly lots of different councils and tribunals dealing with Sharia principles, they aren't courts of law.
Most are Sharia 'councils' set up to make decisions on purely religious matters, although there are some bodies that mix Sharia principles with legally binding arbitration. But none can overrule the regular courts.
Getting married for the purposes of your religion doesn't necessarily mean you are married in the eyes of the state.
Equally, the paperwork required for a civil divorce needn't be recognised by your religion.
For this reason, many Sharia councils exist to issue Islamic divorce certificates, and give advice on other aspects of religious law. They're often attached to mosques.
Family law and Sharia
Other services related to family issues might be offered by a Sharia council. Family mediation is one example.
Some campaigners worry about using mediation by religious bodies to work out agreements about children and finances after a marriage breaks down.
In 2014 Baroness Cox, a member of the House of Lords, tried to introduce a law to ensure that women aren't disadvantaged in mediation by religious bodies, and make clear that they aren't a court.
But, formally, this is already the case.
While feuding couples have to at least consider mediation before going to court, it doesn't override family law. A court has to sign off on any agreement made after divorce for it to be legally binding, and won't do so if the judge thinks it's unfair.
In 2013, the High Court was asked by an Orthodox Jewish couple to accept the ruling of a Jewish religious court on post-divorce family arrangements. The judge said that while the agreement would carry weight, it would be non-binding—neither party could get around English law by agreeing to abide by the decision of another tribunal.
Sharia arbitration bodies
The way Sharia might become legally enforceable is where a Sharia organisation is used for arbitration. This means taking a commercial or personal dispute to a neutral forum and agreeing to be bound by what it decides.
It's up to the people having the dispute who they agree to be the arbiter, and they can even choose to apply rules other than English law to the affair—so long as there is no conflict between the two.
The Muslim Arbitration Tribunal is an example of this approach. It appoints one qualified lawyer and one expert in Islamic law to each case. In this way, it tries to ensure that the decision reached is in line with both secular and religious law.
So if both parties agree, arbitral tribunals can decide certain issues by applying religious principles.
This doesn't make them courts as such. Their legal authority comes from being voluntarily chosen as a decision-maker, and they can't make any decisions that are contrary to national law.
How many of these Sharia organisations exist?
From the research that's been done to date, it's not clear how many exist or how many different types there are.
One piece of research from the University of Reading has identified 30 major councils, and some smaller ones, providing these services.
The UKIP leader Nigel Farage mentioned a figure of 80 on the BBC Radio 4 Today programme in January 2015. UKIP told us that he got his number from the Telegraph article.
But the Civitas estimate includes online forums and admits that the actual number is "indeterminate".
So far as we are aware, there are no definitive studies.
Law versus reality
The coalition government had said that the courts have the powers they need to protect people from coercion and unequal treatment.
But campaigners like Baroness Cox reply that whatever about the strict legal position, "the power of Sharia councils lies in how they are perceived by their communities".
Academics tend to be more relaxed, saying that "fears that councils are forming a parallel legal system appear to be unfounded". A new book by a Dutch researcher is reportedly more critical about how women in particular are treated.
Researchers also stress that we need more information to work out how important Sharia councils are on the ground, and the experiences of people using them.
Similarly, the government now says that "there is evidence of a problem, but we have an inadequate understanding of all the issues involved". It has commissioned a review into whether Sharia is being "misused or applied in a way which is incompatible with the law", to report in 2017.