Nowadays I only ever use surface-drive sockets for this. A brilliant idea - drives on the flats, not the corners, and it's easy to get one fully onto an already mangled hex (much easier than with a standard 6-point socket).
A while back they were fairly common but now they seem to have disappeared (and no-one seems to know about them).
Here's an image I've borrowed to show the concept:
If 11mm is what you're using (I've been using 7/16 A/F but they seem to have gone completely) the only one I've been able to find is here:https://www.ebay.co.uk/sch/consolidated ... 6732.m1684
(Folks with with professional connections will hopefully have much better resources available.)
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)