In 1806 when Lady Charlotte Fitzgerald was successful in calling the title of 'de Roos' (the spelling of the name was altered to 'de Ros' in 1838) out of abeyance in her favour, she became 'suo jure' 21st Baroness and added the surname 'de Ros' on to that of Fitzgerald. The de Roos family has a distinguished lineage dating back to 1264 when the barony was created by writ of summons of Henry III. Robert de Roos, 1st Baron Roos of Helmsley or Hamlake, Yorkshire, then acquired Belvoir through his wife, Isabel, daughter and heiress of William d'Albini of Belvoir. Few peerages have passed through so many heirs female as this one. As a consequence, it had been enjoyed by the Manners, Cecil and Villiers families prior to the Fitzgeralds' succession to the title. It was to fall into abeyance once more in 1939 on the death of Mary Frances, 25th Baroness de Ros, but was again successfully called out of abeyance in 1943 in favour of her eldest daughter, Una Mary, and in 1958 in favour of the latter's granddaughter, Georgiana Angela Maxwell, 27th Baroness de Ros. The present and 28th Baron de Ros is Peter Trevor Maxwell.