 See Siege of Herat.In 1845, McNeill was appointed chairman of the Board of Supervision, entrusted with the working of the new Poor Law (Scotland) Act 1845, a post he occupied for twenty-three years.During the Highland Potato Famine – nearly as disastrous as the Irish Potato Famine – he conducted a special inquiry into the condition of the western Scottish Highlands and Western Isles, during which he personally inspected twenty-seven of the most distressed parishes.