Baron Lucas is a title that has been created twice in the Peerage of England. The second creation is extant and is currently held with the title Lord Dingwall in the Peerage of Scotland.
The title Baron Lucas, of Shenfield in the County of Essex, was created 13 January 1645 for Sir John Lucas, a Royalist army officer. He was succeeded according to a special remainder in the letters patent by his nephew, Charles Lucas. The title became extinct on the death of the third Baron in 1705.
The title Baron Lucas, of Crudwell in the County of Wiltshire, was created at the request of John Lucas, her father, in 1663 for Mary, Countess of Kent, new wife of the 11th Earl of Kent and only surviving child of the 1st Baron of the first creation above. The title was created with remainder to her heirs male by Lord Kent and failing which to her heirs general without division (the latter being the same way that the Crown passes, i.e. to the eldest daughter in the absence of sons, rather than going into abeyance or to the nearest male-line relative). The 1st Baroness was succeeded by her son, who had already succeeded as 12th Earl of Kent, and who was successively created Marquess of Kent and Duke of Kent. (See Duke of Kent for information on the Kent peerages.)
In 1718, the Duke of Kent's eldest son, Anthony, Earl of Harold (1695–1723), was summoned to Parliament by a writ in acceleration as Baron Lucas, and is usually numbered as the 3rd Baron (see note below). In view of the death of both his sons and the consequent extinction of the dukedom at his death the Duke managed to obtain in 1740 (at the cost of his other Grey titles excluding Lucas) only a new marquessate, Marquess Grey. However he obtained a special remainder of the marquessate, in default of his heirs male, to his granddaughter, Jemima Campbell (who was the daughter and only surviving child of his eldest daughter, the former Lady Amabel Grey, who was the late wife of Lord Glenorchy (later 3rd Earl of Breadalbane and Holland)). On the Duke's death later that year, the Barony of Lucas, along with the Marquessate of Grey, passed to this granddaughter (by now the wife of the 2nd Earl of Hardwicke), who became 2nd Marchioness Grey and 4th Baroness Lucas of Crudwell.