The law does not refer to "Undertaking", That is just a common-usage colloquialism that everybody understands even if the pedents pretend not to , it refers to overtaking on the left.
The HC gives examples of when it is acceptable to overtake on the left, it also advises that Overtaking (Presumable regardless of on which side it is attempted) at junctions is ill advised and qualifies as a "Do Not" precisely because doing so is likley to result in situations like this from arising.
The HC is NOT the law is a guide. "Do not" is NOT "MUST NOT"
Again I will reiterate the Cyclist is a moron. But I'd still maintain that the onus was on the car to cross the path of another road user safely..
Did the cyclist overtake/undertake or did the he carry on at the speed he was doing whilst the traffic in front slowed to a standstill.
The car made a manoeuvre that we probably all do from time to time without the misfortune of cutting someone off. Its just this time the driver got caught out.
Has anything actually come of the accident. Police/ insurance involvment