If you were in the desperate position of needing brain surgery, would you be content for someone with no medical training, but who had seen quite a few brain operations, to carry out yours?
Maybe you'd decline the help of the talented amateur.
Let's face it, there isn't much of a history of successful brain surgery by non-medics.
But what if you were in the different but also desperate situation of trying to get a judge to allow you contact with your children, or attempting to get a court to agree to them living with you, following the breakdown of a relationship?
Would you be happy to use the services of someone with no legal qualifications, no insurance and who was not part of a regulated body? Well, here the talented amateur has something of a track record.
He or she also has a title - they are your McKenzie friend.
In 1970, Levine McKenzie was getting divorced and wanted Australian barrister Ian Hanger, who wasn't qualified to practise here, to sit next to him in court, prompt, take notes and suggest questions in cross-examination.
The judge ordered Hanger to sit in the public gallery and advise McKenzie only during adjournments. McKenzie lost and appealed.
The Court of Appeal ruled that he had been denied help he was entitled to and ordered a retrial. The McKenzie friend was born.
Legal aid cuts
For decades they were largely relatives, family friends, law students or charities helping out free.
Such McKenzie friends still operate, but in April 2013 the market in fee-charging McKenzie friends got a turbo boost from the government.
It cut legal aid from a range of areas of civil law, including most family cases involving divorce, child contact and residence, as well as debt, housing, immigration, welfare and employment.
That left many with a stark choice. Go to court on your own or, if you can't afford a lawyer, phone a McKenzie friend.
Without much fanfare, McKenzie friends charging between £16 and £90 an hour have become an important part of the civil justice landscape.
Although their role is supposed to be limited, they are increasingly mirroring the end-to-end service traditionally supplied by qualified lawyers.
They are not allowed to conduct litigation, but there seems little to stop them advising and drafting documents in a way that amounts to the same thing.
And while they do not have rights of audience in court, many told me that if they ask to address the court and their client wants it, the judge generally agrees.
- Lay advisers who provide moral support for litigants, take notes, help with case papers and give advice on conduct of a case.
- Role set out most clearly in the eponymous 1970 divorce case McKenzie v McKenzie, where the husband was representing himself and wanted the help of someone who was not legally qualified at court.
- Traditionally, they have been family members or acquaintances, who provided help free of charge.
- With increased demand, charging has become more common.
- McKenzie friends cannot conduct litigation, address the court or sign court documents.
This April, in the first major report on fee-charging McKenzie friends, the Legal Services Consumer Panel summed up the divergence of views on them.
"One school of thought is that they improve access to justice by providing valuable support for litigants in person.
"Another view worries that such McKenzie friends may provide poor advice that harms their client and third parties, offer little in the way of consumer protection, prey on the vulnerable and exploit litigants as parrots to promote personal causes."
But who are they, this group of friends?
Some are professionals with experience of the justice system, such as former social workers or police officers.
Others have come to it through experience.
On a Monday night in a dingy function room with a broken door, at the rear of a vast pub in the City of London, I watch six men, all fathers, file into a meeting organised by Families Need Fathers, a registered UK charity that provides support to parents, mainly dads, who've divorced and are seeking contact with their children.
In the bar outside, City types slake their thirst. In the room, the men seek a different kind of solace and support from two McKenzie friends.
Both are veterans of titanic family cases of their own, qualified in the court of hard knocks.
They take details of cases, advise and share their knowledge of court forms, applications, judges and tactics.
It feels like triage, military doctors tending to the scarred and wounded of the family justice battlefield.
Their "clients" are generally grateful and full of praise for the help they receive.
Tom, a chef on low pay, told me that his wife made allegations of violence against him, before leaving the family home with his daughter.
The police released him without charge, but while his wife got legal aid, he didn't and used what money he had for a McKenzie friend.
Without his help, Tom believes he would not have seen his daughter again.
In the largely "post legal aid" civil courts, judges seem to regard McKenzies as their friends too.
Speaking frankly to me, some have confessed that is because something in the way of legal representation is better than nothing.
But they also acknowledge that, in the pressure-cooker atmosphere of family disputes, McKenzies do help litigants separate emotion from fact and can really help focus on the issues and progress cases.
It's entirely unrepresentative, but when I put a request on the BBC website for people to write in with their experience of McKenzie friends, those moved to respond were mainly positive.
Family lawyers had led me to believe that while some McKenzies were competent, many were more often agenda-driven, aggressive and dangerous by reason of lack of knowledge.
However, when pressed, few were able to give hard details.
There are clearly some rogues working as McKenzies and some worrying stories.
Privacy and data protection are issues. Clients' personal details have been put on social media or disclosed inadvertently through client testimonials.
I have been told of aggressive and intimidating behaviour by McKenzies.
And McKenzies themselves voiced concern that some of their number push their own agendas at the expense of the client's interests.
Recently retired High Court family judge Sir Mark Hedley generally welcomes the involvement of McKenzies, but told me: "Some have a deep animus against the family court and they're not anxious to conceal it.
"They can interrupt repeatedly and it really does the person they represent no good at all. It depends on the ability of the judge to control it."
There are good and bad McKenzies, just as there are good and bad solicitors and barristers.
The difference is that the client has remedies against the latter through professional bodies, regulators and ombudsmen.
The Legal Services Consumer Panel Report concludes that fee-charging McKenzie friends should be viewed as a source of potentially valuable support that improves access to justice and contributes to more just outcomes.
Though lawyers may find this extraordinary, it doesn't favour regulation, because the cost and administrative burden could drive McKenzies from the market or put their prices out of reach of consumers who use them for affordability.
Some, especially in the legal world, would say those are expedient conclusions driven by the near decimation of legal aid in civil cases.
But perhaps they haven't found themselves in the new world of litigation, with a broken family, little money and in need of a "friend".