I'll reiterate that the point I made is about complying with the Highway Code. Here's part of a different HC rule, Rule 163 on overtaking, edited to keep to my point.
https://www.gov.uk/using-the-road-159-t ... 162-to-169
... give ... cyclists ... at least as much room as you would when overtaking a car
That was always criticised as being meaningless, or at least ambiguous, as many drivers overtake other cars leaving a narrow margin, so presumably to avoid rewriting it, an illustration has been added. Some riders believe that creates a legal requirement, when it's only advice.
What I tried to get across in my OP and subsequently is that the HC is at the heart of many prosecutions after a crash. A contested prosecution for causing death by dangerous driving will be heard by a jury. A hypothetical case might involve a rider on a busy, rural main road, where the rider was hit and killed by an overtaking lorry. Part of the prosecution case would probably be based on Rule 163, because overtaking with the margin shown in the illustration would have prevented any risk of collision. The defence might be some version of the rider suddenly and unexpectedly joining the main carriageway. I'm suggesting that, apart from any probable prejudice about helmets and against cyclists more generally, any demonstrable ignoring of the HC by the deceased is something for the defence to latch onto when urging the jury to acquit.
We have no certain way of knowing how juries reach verdicts, but I hope that even those who are convinced that I am talking rubbish will accept that the conviction rate for killing cyclists is disturbingly low. (At least from the POV of cyclists and their families.)