During his time in parliament, he acted as a whip for the Irish Unionist Party in the House of Commons for 15 years, and was a strong opponent of Home Rule.

In response, Lonsdale, while sitting as MP for Mid Armagh and member of the Ulster Unionist Council, claimed that the Gaelic movement which supported the Irish language was simply inspired by hatred of England and all things English.

A keen golfer, Lord Armaghdale presented the Lonsdale Cup to the County Armagh Golf Club.

The Lady Armaghdale is the name of a steam locomotive on public display in the Engine House at Highley in Shropshire on the Severn Valley Railway.

The replacement locomotive was repainted in a vivid cherry red and the Lady Armaghdale nameplates were fixed to the water tanks.

Below the window, a memorial tablet with fine Roman lettering was erected which includes his Achievement of Arms.