John Darwin Missing Canoeist

How was missing canoeist John Darwin able to get in and out of Britain without anyone noticing?
Darwin was declared legally dead, so surely his passport would have been invalid. If it wasn’t, did it not show up on the computers that he was still using it?
How many other “dead” people are entering and leaving Britain unnoticed? In the post-9/11 world, with terroist threats everywhere, it’s hard to believe this is going on.
Illegal immigrants are different. They stowaway on trucks and ferries from Europe and risk their lives. John Darwin wasn’t doing that.
I haven’t heard that John Darwin was using a fake passport, and, by the way he and his wife bungled the whole scam, I don’t think they were clever enough to arrange fake passports.
All the scum and no goods from Africa et al manage perfectly ok
Darwin Trial – The True Story