I was reading a bad story the other day and knew I was in trouble when page 1 introduced a character called "Lord Royce Sutcliffe, Viscount of Wrighton". That is wrong in so many ways1
. So here's a short, incomplete sketch of when you can call someone Lord, in the English system of nobility
. (The Scottish system is very similar.)
First, there is no such rank or title as Lord. A person doesn't become a lord as such. It is rather a style by which you address or refer to someone who holds some other rank. Second, not everyone who is styled Lord is a lord.
"A lord" means a peer or a noble or a nobleman. (This is largely about men, and the titles of women can be derived from those of men; I shall largely ignore them.) These are the people who inherit their lordships, or are given a new lordship for exceptional merit or favour, and who traditionally sat as legislators in the House of Lords, though recently this privilege has been removed from the British constitution. In modern times (since 1958) there have been non-hereditary life peers, but they're barons and this all applies to them as such.
There are five ranks of lord, from top to bottom Duke, Marquess, Earl, Viscount, and Baron. (Marquess can also be written Marquis but -ess is now the preferred spelling in England.) This is what I mean by saying there is no rank of Lord as such. There are five ranks. A lord is any one of those five. (But this is the English system: in Scotland the barons haven't sat in Parliament since 15942, the equivalent legislative title being Lord of Parliament, so in effect there are just plain lords in Scotland. Sorry, if you're easily confused you shouldn't be reading this node.)
A title consists of this rank plus a name, traditionally a territorial name, but in modern creations often just a surname: e.g. the Duke of Devonshire, the Marquess of Manchester, the Earl of Exeter, Viscount Ventnor, Baron Blakemore.
Dukes are always of somewhere, and Marquesses and Earls usually are, though there are some without 'of', such as Earl Grey and Earl Rivers. Viscounts and Barons never have 'of' after the title.
All except Dukes are usually known as Lord So-and-so. The Earl of Exeter is known as Lord Exeter, Viscount Ventnor is known as Lord Ventnor. Barons always are: it is extremely formal and unusual to refer to Lord Blakemore as Baron Blakemore. The style 'Lord' never has an 'of': the Earl of Exeter is not styled Lord of Exeter. (No-one in the English system is ever styled Lord of Somewhere, though they can be in Scotland.)
A title is a possession of an individual. Often a high-ranking lord will have several titles. In this case his eldest son is styled by his father's second-highest title, as if he holds it. But he doesn't: it is a courtesy title only, and the son is a commoner until he actually inherits from his father. (Of course, it's possible the son could be granted an entirely separate title of his own as a reward for merit.)
Younger sons are commoners also but they are styled Lord Forename Surname if their father is a Duke or Marquess. It is important to note that they are not a Lord, despite being prefixed with that word. Only non-lord younger sons are styled with a forename and surname like that. Younger sons of Earls, Viscounts, and Barons are styled The Honourable Forename Surname. For example, Dorothy Sayers's fictional Lord Peter Wimsey is well known: you can tell he isn't a lord, he's the son of one.
Females: the female titles are Duchess, Marchioness, Countess, Viscountess, Baroness. Usually these refer to the wife of the title-holder, but a small minority of titles were created with a remainder (formula for who can inherit) allowing female inheritance. In this case, the husband of e.g. the Countess of Mar in her own right does not gain any rank or style from being married to a countess. Although barons are never normally styled Baron, baronesses in their own right are usually, e.g. Baroness Thatcher, because the title Lady can refer to a number of other kinds of person. But Marchionesses, Countesses and Viscountesses are usually styled Lady So-and-so, just as their husbands or fathers are styled Lord So-and-so.
All the daughters of Dukes, Marquesses, and Earls are styled Lady Forename Surname. Again, if you read of e.g. Lady Caroline Lamb you know from the style that she is not a title-holder, but the daughter of one. The daughters of Viscounts and Barons are styled Honourable like their brothers.
You sometimes see advertisements offering to buy a genuine title: become a real lord! These are fraudulent or almost so. You can't buy a peerage. (Well, a million pounds to party head office might help.) If these are genuine English titles, it is lord of the manor, which is not a title of nobility, just a hangover from the feudal period. You can buy or sell those and leave them to your heirs or to the postman, but they're meaningless. A lord of the manor isn't a lord.
There are a few others: some bishops and judges get ex officio into the House of Lords, and they get the style Lord, but are not nobility. In Scotland, some other judges are styled Lord by virtue of their position, but without membership of the Lords.
Knights are not nobles, but I'll digress with a brief note on their titles. A knight gets the prefix Sir, e.g. Sir Isaac Newton, or for short Sir Isaac (not Sir Newton!). A female knight is Dame, e.g. Dame Felicity Lott, but the wife of a knight is Lady His-surname-only, e.g. Lady Newton (not that there was one in his case). It is incorrect to refer to her as either Lady Anne Newton, or Lady Isaac Newton.
No-one is officially styled with just a forename: no Lord John or Lady Anne, though they may be more casually called this just as Mrs Anne Smith may be called Anne.
In histories you sometimes see personal names combined with titles, as in Robert Devereux, Earl of Essex, but this is not a correct style but merely a convenience for the historian in sorting out people who should strictly be referred to as either just the Earl of Essex or perhaps "the first Earl of Essex". The ordinal number is never part of the official style, though.
In the case of women you sometimes see dowagers referred to as e.g. Anne, Countess of Bognor. This is because her husband being dead her son is now Earl and her daughter-in-law is therefore the Countess. The previous countess needs some distinguishing style, though the correct one is in fact Dowager Countess of Bognor.
Yet another complication has occurred to me. I have said some ranks take "of" and others don't. However the name part of the title can be compound: there is a Lord Russell of Liverpool, and he is a different person from Lord Russell3. These days many people promoted to life peerages take their surname as their title, but if plain George Brown is so promoted, and there already exists a Lord Brown, the new one has to take a different title. Possibilities include: (i) a territorial title, e.g. Lord Birmingham; (ii) surname "of" territorial, e.g. Lord Brown of Birmingham; or (iii) what the real George Brown did, a hyphenated form, becoming Lord George-Brown. The reason he wasn't allowed to become Lord George Brown (unhyphenated) is that this makes him look like a younger son. This is also the reason why Andrew Lloyd Webber acquired a hyphen when he became Lord Lloyd-Webber.
Someone who holds, say, a dukedom and an earldom is styled by the higher-ranking one, the dukedom, and the other one is not mentioned. But if they hold two of the same rank they are known by both, e.g. the Duke of Buccleuch and Queensberry, or the Earl of Mar and Kellie.
1. Okay, let's count them. (1) If he's Lord Forename Surname then he doesn't hold a title, so can't be a viscount; and vice versa. (2) "Royce" in the Regency period!? (3) If you're Viscount Wrighton you're called Lord Wrighton, not Lord Anything-else. (4) You can't be Viscount of anything. (5) Wrighton is an impossible name for a place: it's a mixture of a real place name like Brighton, ending in -ton "town", and of a surname Wright. Towns do not get named after humble artisans like wrights.
2. See http://www.scotsgenealogy.com/online/baronage_of_scotland.htm for a lot on Scots barons
3. A further complication. Every peerage when it is created is assigned to a town or village in a county, and so described in the letters patent creating it, for example "of Winchelsea in the County of Sussex". This is not part of the title. With a compound title like "Russell of Liverpool", the letters patent name him as e.g. Baron Russell of Liverpool of Winchelsea in the County of Sussex.