thanks georgie, i should know better by now.
usual routine particularly on hols, is factor 50+ all over half an hour before even setting foot outside, large floppy wide brimmed cricket hat, reapply factor 50 + on arrival at pool/sunbed, reapply every half hour regardless. and it usually works. on the last cruise i even came back a little brown ish.
my sister on the other hand takes after my late mother applies chip fat/oil and lies in sun for 12 hours till crispy and doesnt burn at all 2 days and shes got a perfect tan.