"Hello GMES",
I have not read all of he replies so sorry if this has already been mentioned - and am sure that you thought of this at the time but just in case:
Unless there was a problem in early November with the postal deliveries in your area you should have received 2 separate Vehicle Excise Duty reminders - one for each Vehicle that needed renewing at the end of November.
Even if ONE was e `lost in the post` I would doubt that 2 were.
I agree that the Tax Disc was a good reminder - but the DVLA decided they could save a lot of money by abolishing it.
I think that You have been VERY Lucky no to have been caught by a ANPR Camera / Police Car ANPR Camera.
We have ANPR Vans constantly driving around the Streets in the area of South London where I live - they find Untaxed or Uninsured vehicles [or unpaid Parking Tickets]and immediately clamp them and arrange for them to be removed by being lifted onto a lorry.
"Happy New Year"
Regards,
Chris