As far as I can make out with reference to the Grauniad/Barclays tax evasion dossier:
1) Barclays has done nothing illegal
2) Barclays hasn’t receieved any aid from the UK taxpayer.
…so this isn’t an issue.
Should Barclays request aid from the UK taxpayer at any point, its activities should, obviously, be taken into account when deciding how much of a haircut its shareholders deserve to be given. But at the moment, it’s trying to stop the UK taxpayer from making it take ‘aid’, which is kind-of the opposite…