The amount of "could"'s being thrown around in that article.
"They could maybe perhaps be thinking about potentially doing that at some point, if perhaps we somehow fail to stop them, maybe".
Pure fear mongering. There was no reason for him to give that interview. I guess he just wants to be seen as the hero that protected the UK when nothing happens.
Thatcher is the last person May should try to emulate if she wants to crack down on terrorism, Thatcher was terrible at dealing with the IRA.