A party hijacked by purists is straight out of Daily Mail speak. Labour has not been infiltrated, hijacked, bushwhacked or taken over.
If you're looking for entryists, look no further than the New Labour crowd, Blair and Brown convinced the Labour Party that the problem it had with the electorate was the party itself and so they eradicated the old party and set up New Labour, the fresh new third way alternative.
Labour is re-emerging from the tory-lite soup of the third way, while trying to come to terms with the death rattle of Blairism.
It's not complicated, it's not rocket science and this explanation of what is happening has one overwhelming thing going for it, it is the unalloyed truth.