Easiest thing we found worked was a provisional driving license. Carrying a passport around is tricky for DS who tends to misplace things. DD still gets asked for proof, she's 25 but looks much younger.
That's brilliant, thank you. Didn`t think about that, one ds has one as he is currently having lessons, my other ds is at an Army foundation college so not sure whats happening there re driving, my dd wants lessons next so will get her her provisional. Sorted, thanks!