The 21, and why it’s 6-6-9

The deck a player actually deduces with is exactly 21 cards: one for each of the six suspects, one for each of the six weapons, and one for each of the nine rooms. Note what isn’t a card — the victim. In the British game that’s Dr Black (Mr Boddy in North American Clue); he’s the body, not a suspect.

The asymmetry — six, six, then a jump to nine — isn’t arbitrary. It falls straight out of the board. Anthony Pratt designed a country-house floor plan with nine rooms, so there had to be nine room cards; the suspects and weapons were trimmed down to a tidy six apiece around them.

A murder mystery for the blackout

Cluedo was devised in 1943 by Anthony E. Pratt, a Birmingham pianist who had played hotels and cruise ships before the war put him on a factory line making components for tanks. The murder-mystery dinner parties he used to perform at had stopped; the game was his way of bottling that evening’s entertainment for the home, designed during air-raid blackouts with help from his wife Elva, who is credited with the board.

He patented it as “Murder!” — patent GB586817, granted on 1 April 1947 — and demonstrated it to Waddingtons in early 1945. It was Waddingtons that renamed it Cluedo, a portmanteau of “Clue” and “Ludo” (Latin for “I play”, and the name of a board game they were already selling well). Post-war material shortages held the launch back to 1949; in the US, Parker Brothers published the same game as Clue.

The cards that didn’t make the box

Pratt’s prototype was busier than the game you know. His draft ran to roughly ten suspects— names like Mr Brown, Mr Gold and Miss Silver alongside the survivors — and a noticeably deadlier armoury. Among the weapons he proposed but that were cut were a syringe, an axe, poison and a bomb. The board also lost rooms, including a gun room and a playable cellar.

Waddingtons pared all of it back to six colour-coded suspects, six household weapons and nine rooms — the shape that has barely moved in 75 years. The explorer above lets you flip between the survivors and the casualties of that edit.

Why exactly 21 works

The number isn’t just decorative — it’s the engine. Three cards (one suspect, one weapon, one room) go into the envelope as the solution; the remaining 18 are dealt to players as the alibis you eliminate. With three to six players, 18 deal-able cards split into hands that make the deduction tight but solvable. Try the envelope below.

21 is the classic — not the only — count

That 21 is the classic set. Expanded versions move the goalposts: Clue Master Detective adds extra suspects, weapons and rooms, and some later editions sprinkle in card types the original never had — Clock cards, Intrigue cards and the like. If you’re counting a themed or deluxe box, expect the total to climb past 21.

As for the man behind it: Pratt sold the international rights for £5,000 in 1953 and drew UK royalties only until the patent lapsed in 1967. He slipped into obscurity so completely that when Waddingtons went looking for him around the game’s 150-millionth sale in 1996, they discovered he had died two years earlier. A plaque finally went up in his honour at 9 Stanley Road, Kings Heath, in 2013.

Sources

• Victoria & Albert Museum, collection record for the early-1950s Cluedo set — six characters, six weapons, nine rooms; Elva Pratt’s board.
• Wikipedia, “Anthony E. Pratt” — 1943 origin, “Murder!” title, patent GB586817 (1947), the Clue/Ludo naming, £5,000 sale in 1953, rediscovery in 1996, 2013 plaque.
• Wikipedia / Cluepedia, “Cluedo (1949 edition)” — the 21-card composition and original weapon list.
• Mojo Nation, “Cluedo at 75” and People of Play, “Clue/Cluedo” — Pratt’s wartime factory work, cut suspects and weapons, Waddingtons’ changes.

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