Free Traffic Legal Advice

Yes.

Respond naming Robert as "the person keeping the vehicle". He will then receive a s172 request in his own name, requiring him to name the driver.

BTW was this "someone else" insured to drive the car? If not, Robert has committed another offence.

No, not insured.

However, they may be insured under their own policy else?

Any DOV cover could be problematic.

It is commonly the case that they need the permission of the owner.

It shouldn't be an issue for you.

In my non comprehensive sample of 2 one says "... private motor vehicle ..." the other "... another car ...".

But yes, it can be either. Though in this case with no  permission from the owner it's unlikely to help.

Of course, if Robert simply nominates the actual driver the likely insurance issue may well pass unnoticed.

Personally I don't see any real reason for OP not to just nominate "Roberts mate" provided he can still do so in good faith, though I would get Robert to produce a statement for the corporate records.

I understand OPs reluctance of course. Especially if there is a non UK licence or address involved.

Personally I don't see any real reason for OP not to just nominate "Roberts mate" provided he can still do so in good faith, though I would get Robert to produce a statement for the corporate records.

I think you have given a reason as to why he can't just name Robert's mate. The OP wasn't the keeper of the vehicle at the time of the offence, Robert was. Only Robert can honestly testify that he gave his mate the keys. What if his mate responds to the OP naming him as driver with 'it wasn't me'?

Seems like a lot of hassle can be easily avoided by just naming 'Robert'

I disagree. In the context of this thread, Robert appears to be the PKV. Unless Robert was a passenger in the car while his imaginary friend was driving, he cannot know for certain that his imaginary friend was indeed driving at the material time. What he can know is whether he gave the keys to his imaginary friend, and possibly saw his imaginary friend drive off.

The handing over of the keys (by Robert to his imaginary friend) is relevant insofar as most cars are somewhat difficult to drive without the keys, but beyond that I would suggest that it is irrelevant to the OP's obligation.

If we can assume that the OP is not the PKV, then his obligation, when so required is to provide any information that is in power to give and that might lead to the identification of the driver. If there is a likelihood that this will go south, then it would seem appropriate to ensure that he dots the "i"s and crosses the "t"s.

The information that is in his power to give would appear to be that the vehicle was assigned to Robert (Robert was the PKV), and that Robert has informed him that <name of imaginary friend> was driving at the material time.

However, without seeing the notice, it is not possible to determine what exactly is being asked of the OP - merely to nominate the keeper of the vehicle, or chapter and verse.

Thanks all - an interesting discussion for sure.

I think the language on the NIP is of note, I've taken a photo of the relevant bit, which may feed the discussion a touch. It's attached to this post.

We have named Robert as the "possible driver", and it's now up to him to thrash it with the police.

I hope you said a bit more than that, i.e. explained the relationship and that Robert was keeping the vehicle.

Simply naming someone as the "possible keeper" would see you prosecuted.

But I can't do anything but name the "possible driver" - look at the title of Section 4

Here is a photo of the section of the NIP in question - https://ibb.co/zPBTp21