the danger of sitting under trees

john and me just had a rather dissapointing lunch on the library lawn. we sat under a tree eating our horrible 'wraps', and crisps (john also had a coke, but i didn't). i got shat on by a bird (of the feathered kind) -- the effluent seems to be indellible. i've tried washing it off to no avail. john suggests that it may be down to the type of berries our avian friend may have been eating. cheers john