In reply to Milesy:
> (In reply to off-duty)
> [...]
>
> +1 to this.
>
> I find it very hard to believe the authenticity of this email. Look at the email headers and see who the "from" and "reply to" headers are set to. Sometimes the "from" is spoofed to a fake address so it looks to be from as legitimate source but when you click reply it is going to a different hotmail address or something.
Agree - my first thought would be suspicious - scammers trying to glean personal info.
Did the email have the details? Flight number, times etc? Or was it vague (you were on a flight to London in the last 6 months?).
This could be genuine, but I think you'd be within your rights to be mistrustful.
The only way to be sure is to call the met police and ask to talk to the officer concerned.
Don't communicate back to the original email address.
If it's genuine, they will not be annoyed that you're taking precautions, if its not, they'll be able to tell you and you'll be able to complain about the scam which might be happening to other people.