Only a peer may be said to hold a title "in his/her own right." All other titles are courtesy titles(88).
The 1st Duke of Marlborough's eldest daughter, who inherited her father's peerage (via Parliamentary and royal warrant), was Duchess of Marlborough in her own right. But before her father died, she was not Lady Henrietta "in her own right." She was Lady Henrietta by courtesy. When her husband became the Earl of Godolphin, she was the Countess of Godolphin by courtesy (even though she was then called a "peeress"). Her husband, the earl, did not become Duke of Marlborough by courtesy; he remained a mere earl (much like the husband of a queen is not a king by courtesy)-- husbands of peeresses in their own right are not granted the use of the title for themselves. When a woman holds a title in her own right, she is said to be, for example, suo jure Countess of Mar.
However, before the Peerage Act of 1963, husbands of peeresses acquired an important right from their wives' peerages: they executed any hereditary office which accompanied their wives' peerages. For example, in 1818 Lady Willoughby de Eresby's husband fulfilled her role as Hereditary Great Chamberlain of England.(88) Today, presumably, the suo jure Lady Willboughby de Eresby fulfills that role herself, as well as sitting in the House of Lords.
There are currently eight females holding hereditary baronies in their own right: Ladies Berners, Braye, Dacre, D'Arcy de Knayth, Dudley, Strange, Wharton, and Willoughby de Eresby.(89) (The latter is the same barony which Mr. Drummond-Burrell, the husband of the haughty Almack's patroness, inherited in 1828.(90) )
Additionally, most Scottish peerages, like the ancient English baronies, allow the peerage to pass to the "heirs general," so females can inherit them. Lady Herries, Lady Kinloss, Lady Saltoun of Abernethy (all the preceding are baronesses), Lady Mar, Lady Loudon, Lady Dysart, and Lady Sutherland (the last four are countesses) are current examples.(91) (Scottish baronesses are addressed in the House of Lords as "the Noble Lady" rather than "the Noble Baroness," the form of address for all other baronesses.)(92) Countess Mountbatten of Burma is one of two daughters of Louis Mountbatten, created 1st Earl Mountbatten of Burma (who was killed by an IRA bomb in 1979), and is probably the first peerage created in nearly 300 years with a remedy to daughters (the next most recent being the Dukedom of Marlborough).(93) (There was at least one peerage, the earldom of Mansfield, created in 1776 with a remedy to a specific woman, though not a daughter, who became suo jure Countess of Mansfield in 1793, but the circumstances surrounding this patent are complicated.(93a))
There are currently no duchesses, marchionesses, or viscountesses in their own right.(94)
Interestingly enough, when a woman inherits a peerage which devolves upon the heirs general (as opposed to one created by letters patent with a special remedy to a [usually specific] woman), it is not because she is eldest. When the incumbent (or heir) of one of these peerages dies and leaves only daughters, all the daughters have equal right to the title.(95) What happens is that the title "goes into abeyance" until the Queen (the Lord Chancellor) "terminates" the title in favor of one of them. It does not have to be the eldest. There have been times when a title has gone into abeyance for a hundred years or more.(96)
Also, like the monarchy itself, these ancient baronies still devolve upon daughters even if there are other heirs male available. For example, the late Baroness de Ros was the 27th incumbent of the oldest barony of all, dating back to 1264. Her grandmother, Una Mary, who also held the barony, had two sons. She died in 1956. The eldest son, Peter, had predeceased her, but left two daughters. The barony thus went to one of the daughters, not to their uncle, Una Mary's second son (who, by the way, was also a Baron--three times over--and held the second-oldest barony, Mowbray, dating back to 1283 [and of course there is a dispute of which is really oldest, due to circumstances I will not detail], and he was thus called the "Premier Baron," with an asterisk next to his name on the official rolls, noting that the Premier Barony was actually held by Lady de Ros).(97)
Another example is the Countess of Sutherland. In 1766 the 18th Earl of Sutherland died leaving only an infant daughter.(98) The title is Scottish, and the most ancient peerage in Britain, dating from about 1235 by writ (or 1275, or 1061, depending upon the source), so it could devolve upon the heirs general.(99) After a challenge by two other claimants to the title, the House of Lords found for the baby girl, who became the Countess of Sutherland in her own right, or suo jure. She married in 1785 the heir of the Marquess of Stafford; he was later created 1st Duke of Sutherland in 1833, a few months before his death. Their son, known as Earl Gower before his father was created a duke, thus inherited the dukedom in 1833, but did not inherit the Earldom of Sutherland until his mother died in 1839.(100)
Since the dukedom was created in the peerage of the United Kingdom in 1833, it was done by Letters Patent which specified the heirs male. A century later, the 5th Duke of Sutherland's only male heir was a distant cousin, but he had a niece, the only surviving child of his only brother. Thus when the 5th Duke died in 1963, his niece inherited the Scottish peerage and titles (and all of his land), while the peerage of Great Britain (the dukedom) went to the heir male (and very little else).(101)
The Dukes of Norfolk also hold the Earldom of Arundel, which was created in 1138 (and thus is really the oldest, but is swallowed up by the dukedom) and can be separated from the ducal titles in much the same way.(102)
The Countess of Mar traces her titles back to 1114, but the title recognized for precedence is one created in 1404, so Lady Sutherland takes precedence.(103) (I think Mar's earlier "title" may have been by tenure, see Hereditary Peerages.)
In 1762 Lady Caroline Fox (daughter of 2nd Duke of Richmond and mother of Charles James Fox) was granted an hereditary peerage as Baroness Holland (county Lincoln), while her husband was created Baron Holland of Foxley (county Wiltshire) over a year later. Their son thus actually inherited two baronies.(104)
Pat Matthews mentioned that Anne Boleyn was created a Marchioness in her own right by Henry VIII before he married her. It would be interesting to see whether her daughter Elizabeth inherited the title, for several reasons. First, titles of people executed for treason were often extinguished before (or by) the execution even if the peer had heirs (see discussion of attainder). Second, even when women were created peeresses in their own right, it did not necessarily mean that a daughter could inherit the title. Women inheriting peerages are rare; as discussed above, it depends entirely upon the terms of the original creation. For example, Lady Caroline Fox's Barony of Holland was created with a special remainder, but it specified that the barony was to pass to her sons by her husband, Henry Fox.(105)
Often women who were created peeresses were only given life peerages.(106) This was the case with the Duchess of Portsmouth and the Duchess of Cleveland, both mistresses of Charles II whose sons were created dukes (of Richmond and Grafton, respectively).(107)
The first Duke of Richmond's mother was Louise de Keroualle, who was sent by Louis XIV to the English court to negotiate a peace treaty (she was attending Louis XIV's sister-in-law, who was also Charles II's favorite sister). She ousted Charles II's reigning mistress, and he created her Baroness Petersfield, Countess Farnham, and Duchess of Portsmouth.(108) In recognition of her service, Louis XIV granted her the Stuart family lands in France (Charles was a Stuart, remember), including the estates of Aubigny and La Verrerie. When she retired to the Chateau d'Aubigny, she was known as the Duchesse d'Aubigny.(109)
The son of Charles II and Louise was Charles, who took the surname Lennox. While the son was still an infant, the king created him Baron of Settrington, Earl of March, and Duke of Richmond in the English peerage, and Baron Methuen of Tarbolton, Earl of Narnley, and Duke of Lennox in the Scottish peerage.(110) When his mother died, he added the title of Duc d'Aubigny to the list and did homage to the French crown for it.(111) But he was never the Duke of Portsmouth, or Lord Petersfield or Farnham. Those peerages lived and died with his mother.
(The point is that when talking about titles, we have to remember that the universal statements we make about "how things are" is only true for England, not for other countries, and not necessarily even for Scotland and Ireland.)
On to Dowager Peeresses
Titles of Nobility In Britan
Hereditary Peerages, including Royal Titles
Rights and Privileges of Peers
A Peeress "in her own right"
Entails, Marriage Settlements, and Dower
Correct Forms of Address
The 1st Duke of Marlborough
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