Chris S wrote:

Steve, I agree with all you say and add an observation.

And after thinking about it again, Mr B also has another option. If he
reports to the police that his car has been taken, the police don't even
have to prove theft in order to get a conviction.

Theft requires that the parents have the intent to permanently deprive
Mr B of the car. I'd say that if they had their wits about them they
could argue that they did not intend to steal the car, but to hold it to
force B to pay up and that they fully intended to return the car in good
condition. That is a reasonable defence to a charge of theft. However
the indication in previous posts is that they do intend to permanently
deprive B of the car which is theft.

However even if they do get it right WRT any statements made about
keeping the car or selling it on (i.e. deny that was their intent). They
can still be charged with "Taking Without Owner's Consent" the infamous
"TWOCing" it's far easier to get a conviction for TWOCing than it is to
get one for theft. Net result is still the same whoever took the car
gets a criminal record, DNA on database, etc.

If the parents have anything shady in their past, then getting arrested
for any reason could be a big mistake, since all new DNA samples are
searched against all extant scenes of crime samples. I'm not making
statements about whether they are likely to have a reason to want to
avoid being arrested, I'm saying they really need to think very
carefully about their actions. Not simply to react in anger because of
what has happened.