The Guardian reports:
The cash-for-honours investigation took a fresh twist today as Downing Street was forced to deny claims that it had a secret computer network from which potentially crucial emails had been deleted.
Iain Dale has suggested that we are entering Watergate-type territory. Well, there was a 18.5 minute gap in tape three of the subpoenaed tapes in the Watergate scenario. In the end, it was the unwiped tapes which did for Nixon. However, I doubt whether there will be any emails in the current situation which cannot be recovered.
I am not a techie but I have been immersed in IT and sending/receiving emails for twenty-three years now (yes, email has been around in some form for more than that length of time now). The safest assumption to make is that you cannot delete an email once you have typed it in.
If you gather up all the hard drives of all the people to whom the email was sent, plus presumably the ISPs through whom it was sent, and then use a sledgehammer or an incinerator to physically destroy all those hard drives, then you might have a sporting chance of deleting those emails.
You might think you have deleted the email by "deleting" it on Outlook, for example. But you haven't. As a simple step, the mail can be recovered from the deleted folder. As a more complex step, it can be recovered from your hard drive. And you can't really wipe the hard drive unless you are using extremely serious high-tech industrial specialist software or, indeed, use the proverbial sledgehammer mentioned above.
I very much doubt that anyone on the political side in Downing Street knows how to really delete an email, even if it were possible.
If in doubt, ask Monica Lewinsky about this. She thought she had deleted emails to do with Bill Clinton and "Staingate", but she hadn't. The FBI recovered them. She has said:
They were things that I thought I had deleted. I certainly came to see that obviously I was wrong. While you may think it's deleted, it isn't. I mean it's there permanently.
It is a different matter if, strictly theoretically, someone in Downing Street thinks they have deleted an email which they might conceivably, allegedly and strictly theoretically prefer not to see the light of day. They are probably wrong, and, therefore, could possibly, allegedly, conceivably and strictly theoretically be "cruising for a bruising".