607kts? Bloody hell, that's nearly 700mph! Certainly the FedEx's strobes seemed to be zipping along - I thought it was much lower than it was. Think it was the one DRUK has mentioned, time is about right.
I was a passenger in a C150 once arriving in the circuit over Popham - we seemed to be shifting a bit with 100 on the ASI and I commented on it; mein Kapitan replied "oops, just remembered they've replaced the ASI with one that's knots rather than MPH..."