With regard to "they always check", are you sure? I came accross an opinion they always check insurence on car owner. If a driver is not an owner he might not be checked.

If the 'friend' was given instructions that he could
only use the vehicle on the condition insured it and the owner was
given that assurance then when it was used
because no Insurance was taken out then the owner did not
give permission for the use of the vehicle. In this case there
is no offence of permitting the use of a vehicle without
Insurance. This was the direction in the case
Newbury v Davis [1974].

In relation to speed offences detected by camera it would seem
that they are only interested in that offence and do nothing in
relation to document check. They have Insurance and Excise
details on computor (MIB and DVLA) against vehicle details
and a simple quick check could reveal further offences which could
be included in the 172/Noip sent out. In the case of Insurance
a £200 6 points opportunity lost.(Money Mr Osbourne, money)

dvd

There's a legal requirement for you to name your friend as the driver - once you've done so that's the end of your involvement in the speeding case.

If the police check/pursue the insurance status you'll need to provide a statement giving the details of your conditional permission - this will incriminate your friend but he's in doodoo whichever you do unless the police simply don't bother to check the insurance of the "nominated" driver.