How the Tower of London was built: William's White Tower of 1078, the stone from Caen, the walls of Henry III and Edward I, the moat, and 950 years of fortress, palace, prison and zoo

Architecture · 4 September 2026

The Tower of London was begun by William the Conqueror in 1066 as a timber fort in the south-east corner of the Roman city wall, and its keep, the White Tower, was built between about 1078 and 1100 under Gundulf, bishop of Rochester, of limestone shipped from Caen in Normandy over a core of Kentish ragstone, 27 m high with walls 4.5 m thick, the largest keep in Europe and the first stone castle in England; Henry III wrapped it in a curtain wall with nine towers and a palace in the 1230s and 40s and had it whitewashed, which gave it its name, and Edward I added the outer wall, the moat and the water gate in 1275–85, making it the concentric fortress of 7.3 hectares that stands, with almost nothing built since but the barracks of 1845. It has been a royal palace until the 1500s, the state prison until 1952, the Royal Mint until 1810, the royal menagerie until 1835, the public record office, the arsenal and, since 1661, the home of the Crown Jewels; 3 million people visit it a year. Below: the Normans, the White Tower and how it was built, the two kings who walled it, what it was used for, the prison and the block, the Jewels and the ravens, the numbers and the myths, with the keep's place among castles in how castles were built and the oldest and biggest castles.

1066: the corner of the Roman wall

William landed in September 1066, won at Hastings in October, and came to London in December to be crowned at Westminster on Christmas Day; the city was hostile, and he built three forts to hold it, of which the Tower is the one that lasted, in the angle where the Roman wall of about 200, which still stood, met the Thames, so that two sides were already defended and the third could be an earth rampart and ditch with a timber palisade, the standard Norman motte-and-bailey without the motte. The site commanded the river, the bridge and the city's port, and the Romans' Wardrobe Tower bastion and a stretch of their wall stand inside the Tower today, the oldest things in it. The fort was to frighten the Londoners, William of Poitiers wrote, "against the fickleness of the vast and fierce population". Tower of London.

The White Tower, about 1078–1100

• The builder. Gundulf, a monk of Bec whom William made bishop of Rochester in 1077 and who built Rochester's cathedral and castle, is named by the Textus Roffensis as the man who "by command of King William the Great built the great tower of London"; the design is that of the ducal keep at Rouen, since lost, and of Colchester, begun at the same time and larger.
• The stone. The core of the walls is Kentish ragstone from the Medway quarries, rough grey limestone, with the corners, the windows and the dressings in fine white Caen stone shipped across the Channel from William's Normandy, the stone of most Norman buildings in England; Portland stone replaced much of the Caen in Wren's repairs of the 1660s, and the windows are his.
• The plan. A rectangle 36 by 32 m with the apse of the chapel bulging at the south-east corner and turrets at the other three, one round for the spiral stair, 27 m high to the battlements; three floors, a basement for stores and the well, a first floor entered by an outside timber stair on the south side, since the entrance was kept above the ground for defence, and the great hall and the royal apartments above, each floor divided by a cross wall into two rooms; the walls 4.5 m thick at the base and 3.4 at the top, with the stair, the latrines and the fireplaces inside them.
• The Chapel of St John. On the second floor in the apse, a Norman chapel of 1080 with a barrel vault on round piers and a gallery, the most complete Norman interior in England, where the kings kept vigil and Mary I was betrothed by proxy to Philip of Spain.
• The time. Building went on from about 1078 to about 1100, into William Rufus's reign, with the walls rising about 3 m a year in the working seasons, by masons paid by the crown and labour from the shire; the timber floors and roof, oaks felled in 1080–90 by dendrochronology, went on last, and the tower had a pitched roof, replaced by the flat one and the turret caps in the 1530s.

Henry III's inner wall and Edward I's outer one, 1220–1285

• Richard I and Longchamp, 1189–90. The chancellor William Longchamp spent 2,900 pounds on a wall and ditch to the west while Richard was on crusade, and the Bell Tower is his.
• Henry III, 1220–72. Henry made the Tower a palace and a fortress at once: the Wakefield Tower and the Lanthorn Tower on the river with the royal lodgings between them, the great hall, and, from 1238, a new curtain wall on the north and east enclosing the White Tower with nine towers along it, the Wardrobe, Salt, Broad Arrow, Constable, Martin, Brick, Bowyer, Flint and Devereux towers, and a moat the Londoners called useless; a great gate on the west fell down in 1240 and again in 1241, which the chroniclers said was St Thomas Becket's doing. In 1240 he had the keep whitewashed, and it has been the White Tower since; in 1235 he was given three leopards by the emperor, and the menagerie began.
• Edward I, 1275–85. Edward, the builder of the Welsh castles, spent 21,000 pounds, the most on any castle of his reign, on a second, outer wall all round the fortress, lower than the inner so that both could fire, making the Tower concentric; a new moat 50 m wide dug by the Flemish engineer Walter of Flanders and filled from the river; St Thomas's Tower on the river with the water gate under it, Traitors' Gate, by which prisoners came from Westminster by boat; the Beauchamp Tower; the west entrance through the Lion Tower, the Middle Tower and the Byward Tower with three drawbridges; and the Mint, moved into the outer ward in 1279. The fortress as it stands is Edward's, and nothing has been added to the walls since but the Legge's Mount bastion of the 1680s.

What it was used for

• Palace. The kings lived in the Tower until the Tudors, and every monarch from Richard II to Charles II spent the night before the coronation there and rode from it to Westminster; the palace buildings in the inner ward, the great hall and the royal lodgings, were demolished by the 1600s, and the Wakefield Tower's chamber is what remains.
• Mint. From 1279 to 1810, in Mint Street between the walls, coining England's money, with Isaac Newton as warden and master from 1696 to 1727, chasing counterfeiters.
• Menagerie. From 1235 to 1835, in the Lion Tower at the entrance: leopards, a polar bear that fished in the Thames on a rope, an elephant from Louis IX in 1255 that died in two years, lions whose skulls were found in the moat in 1937, and by 1800 300 animals; moved to the new zoo in Regent's Park in 1835.
• Arsenal, records and observatory. The Ordnance Office stored the nation's arms in the White Tower until 1855, the state records were kept there until 1858, and Flamsteed observed from the north-east turret before Greenwich was built in 1675.
• Prison. Never built as one, and never with cells; state prisoners lived in the towers under guard, Ranulf Flambard the first in 1100, who escaped down a rope, then John Balliol, David II of Scotland and John II of France, Henry VI, murdered in the Wakefield Tower in 1471, the Princes in the Tower in 1483, Thomas More, John Fisher, Anne Boleyn, Catherine Howard, Lady Jane Grey, Elizabeth I for two months in 1554, Walter Raleigh for 13 years, Guy Fawkes, the Jacobite lords, and, last, the Kray twins in 1952 for deserting the army; Rudolf Hess spent four days there in 1941.
• The block. Only ten people were executed inside the Tower, on Tower Green, the privilege of the highborn: Anne Boleyn, Catherine Howard, Jane Grey, Lady Rochford, Margaret Pole, Essex, Hastings, and three others; the rest, hundreds, died in public on Tower Hill outside; and eleven German spies were shot in the moat in 1914–16 and one in 1941.

The Jewels, the ravens and the Warders

The Crown Jewels have been kept at the Tower since 1661, when Charles II had a new set made after Cromwell had melted the old ones down; Colonel Blood nearly stole them in 1671 and was pardoned; they were in the Martin Tower, then the Wakefield, and since 1994 in the Jewel House in the Waterloo Barracks, 23,578 stones in all, the Imperial State Crown with the Black Prince's Ruby and the Cullinan II, the Sovereign's Sceptre with the Cullinan I, the largest cut diamond, and the coronation spoon of 1150, the oldest piece, which the Commonwealth sold and a Royalist bought back. The Yeoman Warders, "Beefeaters", have guarded the Tower since Henry VII in 1485, 32 of them today, retired soldiers of 22 years' service, living inside the walls with their families and locking the gates each night at 9.53 in the Ceremony of the Keys, which has not missed a night in 700 years, including the night a bomb fell in 1941 and delayed it by half an hour. The ravens, seven of them with a spare, are kept by the Ravenmaster with their wings clipped, on the legend that the kingdom falls if they leave; the legend is Victorian, the ravens came in the 1880s, and the Tower has kept them since, with names, ranks and a pension.

The Victorians and since

The Tower had decayed by 1800 into a jumble of warehouses, and the fire of 1841 that destroyed the Grand Storehouse began its restoration: the Waterloo Barracks of 1845 in Gothic replaced the storehouse, Anthony Salvin from 1852 stripped the later buildings from the walls and restored the towers to a medieval look, the moat was drained in 1843 after cholera and is a lawn, and the Tower opened to the public as a monument from the 1850s, with half a million visitors by 1900. In the two world wars it held prisoners and spies, and a bomb of 1940 destroyed the North Bastion; the Jewel House of 1994, the moat's poppies of 2014, the 888,246 of them, and the Superbloom of 2022 are the recent history. It is a World Heritage Site since 1988, with the Royal Armouries in the White Tower and 3 million visitors a year, entering through the Middle Tower as Edward I intended.

The numbers

• White Tower. 36 by 32 m, 27 m to the battlements, 36 with the turrets; walls 4.5 m thick at the base; three floors; begun about 1078, finished about 1100.
• Fortress. 7.3 hectares within the outer wall, 4.9 within the moat's inner edge; 21 towers; the inner wall of Henry III, the outer of Edward I; the moat 50 m wide, dry since 1843.
• Cost. Edward I's works 21,000 pounds, 1275–85; Henry III's about 10,000.
• Prisoners and executions. Some 8,000 prisoners over 850 years; 10 executed inside, 22 in all including the spies; the last prisoners 1952.
• Jewels. 23,578 stones; 140 objects; the Cullinan I of 530 carats.
• Ravens. Seven, plus a spare; the Ravenmaster is a Yeoman Warder.
• Visitors. About 3 million a year; 32 Yeoman Warders; the Ceremony of the Keys nightly at 9.53.

Versions and theories

• Julius Caesar built it. Shakespeare's "Julius Caesar's ill-erected tower" is a medieval legend; the Romans built the wall, and the Normans the Tower.
• The Princes in the Tower were murdered there. Edward V and his brother disappeared in the Tower in 1483 and two skeletons found under a stair in 1674 are in Westminster Abbey; Richard III is the usual suspect, and the case is open.
• It is the most haunted building in England. Anne Boleyn, the Princes, Raleigh and a bear; the Yeoman Warders tell the stories and the visitors pay.
• The ravens are medieval. The first records of ravens kept at the Tower are of the 1880s and the legend of the kingdom's fall is of about 1900; Charles II's astronomer Flamsteed is said to have complained of them, in a story of the 20th century.
• Beefeaters ate beef. Probably from the rations of the royal household, "buffetier" being folk etymology; the name is recorded in 1669.
• The White Tower is white. It was, from Henry III's whitewash of 1240, and again in the 18th century; it is grey stone now, and Wren's Portland windows are whiter than the Kentish rag.

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