Colonel Sir William Mahon served in the Irish Guards and in Germany, Malaysia, Aden, Hong Kong, Pakistan and Spain. He is also a former officer of Her Majestys Bodyguard of the Honourable Corps of Gentlemen at Arms. Having visited Waterloo many times, his boyhood interest in the Peninsular and Waterloo campaigns was rejuvenated by his attach service in Spain. The link between Corunna, Talavera and Waterloo focused in the curious story, full of coincidences, of one largely forgotten young officer, Henry Percy.