The lower water tank is a hinged locker where on the ones I rode were stored the searchlight and extra salvage sheets.If you look closely you can see the securing catch on the lid. The top tank was 400 gallons. The appliance was originally marketed as a Multi-Purpose pump, a combination of pump escape and water tender. Keep safe there.
Are we looking at a conversion from a pump escape configuration to a water tender?
I too have fond memories of the Mk II Cortina - my very first company car at Ford!
Added by Rob Johnson on 01 October 2022.