In reply to Climbing Pieman:
Having seen on 2 occasions recently I'm starting to feel more confident. Apart from the general look and behaviour being slightly different (and it's easy to convince yourself wrongly on those), I feel the most distinctive "tell" is...
- the well defined black stripe running from the bill through the eye with white stripe above
followed by...
- the longer thinner bill with a slight downturn at the end
Obviously these are winter plumage, in summer there will be no difficulty if you're lucky enough to see a SR in summer plumage (I haven't been lucky in that respect).
The other thing to remember (and of course I'm generalising here), chances of a SR being around just because common Redshank are around - low, chances of common Redshank being around when a SR is around - high.
So if it really is a SR, chances are there'll be a common Redshank somewhere around that you can compare it with. If you've got decent views of both and the (relatively small) differences aren't obvious then chances are it's not a SR.
Edit: forgot, if all else fails make it fly away 👎 - white wing bar means common Redshank
Post edited at 20:48