When is it acceptable to undertake? Ie pass on the inside.
When traffic in other lanes are queueing and moving at a slower speed or when instructed to do so by a police officer.
Nope.
Nope - that’s not to say your incorrect, just not the answer I’m looking for 
.
If the answer you want is not the right answer which was given then the question is stupid, can you provide a little bit more info?.
I say on a one way road, when a vehicle is turning right, when a sales rep has taken a call in the middle lane and has had to slow down to find his pen?.
And of course like the highway code tells us when it is safe to do so BUT not when the Police officer who just saw you do it decides it wasnt a safe time to undertake even though you are still alive.
It’s safe to overtake on the left whenever you feel like it. Haven’t read it anywhere, just assumed it from an average days’ driving.
If you drive a Hearse does this class you as an Undertaker whenever you are on the road 
It’s nothing to do with driving. Your supposed to be thinking laterally.
When the undertaker is on holiday??
You would have to over take the undertake…LOL
When walking down the pavement.
I must say Coffe’s clos but he’s not quite their this time (wahey!!!).
OK, 2nd attempt. When passing someone on stairs?
When in a country that drives on the right!
Ahhhhhh. Coffee’s allmost got it AGAIN. On a SPIRAL STAIRCASE.