From the Frequently Asked Questions section of Twitter’s very own help website:

Can I edit a tweet once I post it?
Nope. Once it’s out there, you can’t edit it. You can delete an update by clicking the trash icon on the right end of the update, but you can’t make changes.

This puts Labour whip David Wright’s claim that his tweet about the Conservatives being “scum sucking pigs” was “tinkered with” beyond any doubt.  If he had just admitted that it was too far and said sorry last night this whole thing would have been over within minutes, but, as ever, it is the lying that will nail him. CCHQ are pushing this one aggressively and Pickles has just written to Wright accusing him of breaking the Ministerial Code.

A Minister of the Crown could well be set to be Twitter’s first major political scalp.