In April 1854, Sir William of the 7th Hussars was appointed as Aide-de-Camp to the Earl of St Germans, Lord Lieutenant of Ireland. He served in the Crimean War and during the Indian Rebellion of 1857 he served at Alumbagh and at the Siege of Lucknow, and commanded the 7th Hussars on further operations in India and Nepal. He received a medal and clasp, and was made a Companion of the Order of the Bath (CB) in 1859.