It is a Hornby R5672 Car Loading Ramp. Here I have a ramp for sale.
Hornby Tri-ang L5672 Car Vehicle Loading Ramp
Hornby L5672 Car Loading Ramp Moulding - Grey
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Hornby Triang R229 Maroon Restaurant Car Oo Gauge
Hornby Triang OO Gauge R328 Pullman Brake 3rd Car No 79 Train Carriage