Why Is a Duke's Son Called an Earl? Courtesy Titles Explained

• A courtesy title lets the eldest son of a duke, marquess, or earl use one of his father's lower titles — but it is a social custom only; he remains legally a commoner.
• A courtesy lord cannot sit in the House of Lords, but he can sit in the House of Commons — Viscount Castlereagh did so for 25 years before inheriting his father's marquessate.
• Viscounts and barons almost never have a courtesy title to give their sons, because they usually hold only one peerage; their children are styled 'The Honourable' instead.
• A writ of acceleration could summon an heir to the Lords in a real subsidiary title during his father's lifetime — rare, but used for the future Lord Liverpool in 1803.
• When the substantive peer dies, his courtesy-title son becomes the real peer, and that son's own eldest son then inherits the now-vacant courtesy title.
• A courtesy title's name often has nothing to do with the family surname — the Duke of Wellington's heir is 'Douro', not 'Wellesley'.

The paradox in one real example

On 3 May 1814, Arthur Wellesley was created Duke of Wellington — and, on the very same patent, Marquess of Douro. From that day, his small son, seven-year-old Arthur Richard Wellesley, was known in every drawing room in London as 'the Marquess of Douro'. In the eyes of the law, the boy held no peerage at all. He was, strictly speaking, a commoner wearing a borrowed name — and every duke's, marquess's, and earl's eldest son in Regency England lived under exactly the same arrangement. This is a courtesy title, and it is one of the peerage's stranger inventions: a rank that is entirely real in a ballroom and entirely fictional in law.

Where the spare title comes from

A courtesy title only works because a single peer very often holds several ranks at once — a duke who is also, on paper, a marquess, an earl, a viscount and a baron, all stacked up under one man. Most of the time that pile-up happened slowly, over centuries, as a family was promoted rank by rank or married into a second peerage. Wellington's case is the rare exception: he collected the whole ladder — viscount in 1809, earl and marquess in 1812, duke in 1814 — inside five extraordinary wartime years. Whichever way a family arrived at its spare titles, the principle is the same: the top title is the one the peer actually holds and sits in the House of Lords under, and the next one down is the one he lends, informally, to his heir.

Who gets one, and who doesn't

Only the eldest sons of dukes, marquesses, and earls receive a courtesy title, and only if their father actually holds a second, lower title to spare — if he doesn't, his heir goes by no title at all, plain 'Mr', until the day he inherits. Viscounts and barons are almost always single-title peers with nothing spare to lend, which is why their sons are never 'Lord Anybody' by courtesy; instead they take the style 'The Honourable', covered below. This is also why the same family can look inconsistent from one generation to the next: an earl's grandson might be born a courtesy viscount and grow up assuming his own son will inherit the same arrangement, only for an extinguished secondary title or an unlucky settlement to leave the next generation with nothing to pass on but the surname.

Not a peer: the legal reality behind the name

Whatever a courtesy lord was called at the dinner table, the law was unmoved by it. He could not sit in the House of Lords, could not claim trial by his peers, and held no seat, vote, or privilege that any other commoner lacked. What he could do — and a real, titled peer could not — was sit in the House of Commons and hold ministerial office there.

Robert Stewart is the case to know. When his father was made Earl of Londonderry in August 1796, Stewart became, by courtesy, Viscount Castlereagh — and sat in the Commons under that name for the next twenty-five years, rising to Leader of the House of Commons and Foreign Secretary in 1812, the year he helped assemble the coalition that finally defeated Napoleon. He only became a real peer, the 2nd Marquess of Londonderry, when his father died in April 1821. Even then he kept his Commons seat: Londonderry was an Irish peerage, and an Irish peer who was not elected one of the twenty-eight 'representative peers' could still sit for an English constituency. Castlereagh — Britain's Foreign Secretary for a decade — spent almost the whole of it as, legally, an ordinary Member of Parliament.

The rare workaround: a writ of acceleration

There was one legitimate shortcut into the Lords before a father died: a writ of acceleration, summoning the heir under one of his father's genuine subsidiary titles rather than his courtesy one. It was rare — only around 98 were issued across more than four centuries — but Regency-era politics produced a famous case. Robert Jenkinson was summoned to the Lords as Baron Hawkesbury in November 1803, using one of his father's lesser titles, five years before he inherited the earldom itself in December 1808 and became the 2nd Earl of Liverpool. As Lord Liverpool, he became Prime Minister in 1812 and remained so for the rest of the Regency and years beyond, until 1827 — a career in the Lords that had begun, unusually, while his own father was still alive to see it.

Everyone else: Lord Firstname, Lady Firstname, and 'the Honourable'

The mechanism above only ever applies to one person per generation: the eldest son. Everybody else in a titled family is a simpler, different case — a personal style, not a borrowed peerage.

• Younger sons of dukes and marquesses: 'Lord [First name] [Surname]' — Lord Randolph Churchill, never 'Lord Churchill'.
• Younger sons of earls, and every son of a viscount or baron: 'The Honourable [First name] [Surname]', spoken and written as plain Mr, with 'Hon.' appearing only on envelopes and formal lists.
• Daughters of dukes, marquesses, and earls: 'Lady [First name] [Surname]'.
• Daughters of viscounts and barons: 'The Honourable [First name] [Surname]', exactly like their brothers.

The day it all moves up a generation

When the substantive peer died, his courtesy-title son inherited the real thing — the dukedom, marquessate, or earldom itself, with a seat in the Lords and every legal right that had been missing however many years he'd spent as a courtesy lord. If that new peer already had a son of his own, the vacated courtesy title didn't disappear; it simply moved down to him. And if a courtesy-title holder had died before his own father, leaving a grandson as heir, the title jumped straight to that grandson — because a courtesy title always belongs to whoever currently stands first in line, not to one fixed person.

The Dukes of Norfolk show the cascade at its fullest: the Duke also holds the Earldom of Arundel and the Barony of Maltravers, so his eldest son is 'the Earl of Arundel' — and, should that son have a son of his own before the old Duke dies, a grandson would in turn be 'Lord Maltravers'. Three generations, three names, one actual peer.

A note for writers: the title rarely matches the surname

The easiest way to get this wrong on the page is to assume a courtesy title shares its holder's family name. It usually doesn't. The Duke of Wellington's family name is Wellesley, but his heir is 'the Marquess of Douro' — not 'Wellesley'. The Duke of Devonshire's family name is Cavendish, but his heir is 'the Marquess of Hartington' — not 'Cavendish'. A reader who already knows this will clock the error before the end of the first scene; a reader who doesn't will simply learn, correctly, that aristocratic naming in this period never quite worked the way it looks like it should.

Why it matters in a romance novel

A courtesy lord is a walking contradiction, and contradictions are exactly what plot is made of. He has every social expectation of a peer — the manners, the income assumptions, the deference of a drawing room — with none of a peer's legal protections: no automatic seat, no trial by his equals, nothing that can't still be reshuffled by an angry father, a surprise half-brother, or a secondary title that turns out to have been improperly inherited. He can also sit in the Commons and make himself a public, print-worthy nuisance in a way his own father never could. And because his 'real' name is really his father's, still on loan, a courtesy hero carries a built-in uncertainty about who he will actually turn out to be by the final chapter — precisely the kind of instability a romance novel knows what to do with.

A note on the sources

Sources do not clearly establish whether the Wellington heir used any courtesy title between his father's earldom (1812) and dukedom (1814); this guide only asserts the confirmed 3 May 1814 creation of the Marquess of Douro alongside the dukedom itself. The claim that viscounts and barons 'almost never' have a spare title to lend their heirs is a strong, well-documented pattern rather than an absolute rule; sources describe it as the normal case, and no comprehensive list of exceptions was found, so it is stated here as a general rule rather than a universal one.

Checked against 6 independent sources, September 2026. Where the historical record is genuinely disputed, this page says so rather than picking a side.