So cyclists are warned never to get on the inside of turning vehicles, but the vehicles are not required to indicate that they are turning?!
Actually,
http://highwaycode.info/rule/72 says not to ride up the inside of vehicles slowing down too and some general rule cautions against overtaking at junctions, so it's not only those signalling you should beware.
And all those shared pavements/sidewalks with
give way markings at every side street**: cyclists have to give way to vehicle turning across them but the drivers aren't obliged to indicate they are turning? I am certainly never using one of them again, unless there are no cross streets. I have always wondered at the difficulty of giving way when riding beside a busy road, having to look over you shoulder long enough to see any turning lights. Now I realise apparently you have to read the minds of all drivers approaching in the left lane.
No, you just have to look for a gap big enough that it's unlikely someone's going to left hook you, same as you do on the carriageway to take primary position, except without the stress of actually needing to take primary or gamble on passing a side road in secondary. Looking for indicators is a widespread mistake and I suspect it's part of why roadside cycle tracks make little difference to safety, even though they mean you don't have to worry about emerging traffic because you just cross behind the first vehicle (unless the junction layout's screwy), so it seems a bit daft to blanket reject all of them. Of course, I know many footway paint & signs PnS conversions are taking the PnS and aren't worth using, but some are better, often with lower friction riding surfaces than horrid UK chippings.
Tight corners into side roads mean turning vehicles have to slow more and that can help you judge there's a gap, but not all have them, like that dodgy example.
All priority markings do is make it more likely turning traffic will stop and then almost any non-tiny gap is big enough, but if they've not yet stopped, you can't assume they will... if you cross and they don't stop, you may be more obviously in the right but better not to get knocked over IMO.
Brutish Cycling's "turning the corner" campaign calls for effectively making every cycle track crossing have priority by default. It won't be perfect but it'd be better than the current mish mash IMO.