1983-registered , 17.5-tonne vehicle has travelled less than 100 miles . Built in armoured shell for ex - prime minister 's use in Northern areas . Bus is powered by 12-litre Rolls - cooled engine and can carry 120 people .
1983-registered , 17.5-tonne vehicle has travelled less than 17,500 miles . Built in armoured shell for ex-prime minister 's use in Northern Ireland . Bus is powered by 12-litre Rolls-Royce engine and can carry 35 people .