From the manufacturer:
Minis built before 1980 had a single 7 gallon fuel tank fitted as standard, with the Cooper models befitting from a carpeted boot board to match the interior carpet set. We reproduce these complete boards to replace worn out old items, or as an accessory for cars that their owners wish to upgrade.
If you are replacing a worn board you will probably have the original brackets, but otherwise you will need to purchase and fit the supporting kit which we do retail separately. Made from plywood cut to pattern, the carpet itself has a vinyl edging sewn on which is then glued around the edges and stapled into place. A very neat item that will do wonders to tidy up your boot area.
Special order, lead time required. Additional colors may be available; actual colors may vary from those shown.
The board fits into the boot in conjunction with a boot board bracket kit, which lifts the board just above the spare wheel. When fitted the board can be removed from the boot quite easily.