We are told that nobody escaped from the Tower of London. With a strong central keep and protected by two concentric defensive walls and a moat, the Tower was built in such a way that prisoners, even if they managed to break out of their cells, were unable to make their way to freedom.

But this is not true. Over the centuries several people did escape.

1101 Ranulf Flambard Bishop of Durham made his escape by slipping down a rope smuggled in to him in a wine casket.

1323 Roger Mortimer, Lord of Wigmore, made a daring escape. The deputy constable Gerard d'Alspaye arranged for the garrison to be given drugged wine and while the guards slept, used a crowbar to prise stones from the cell wall enabling Mortimer to scramble out. Together with Mortimer's squire, Richard de Monmouth, they climbed up a wide chimney, across rooftops and down walls using rope ladders, until they reached the marshy banks of the Thames. From there they fled first downriver to Greenwich, then to Porchester and then to France.

1597 The convicted Jesuits John Gerard and John Arden escaped along a rope stretched out across the moat towards the Thames. This was despite their hands having been mangled in the torture chamber.

1660 John Lambert, a Parliamentary general and politician was sent to the Tower on 3rd March 1660 but escaped a month later by climbing down a silk rope. He was assisted by six men and taken away in a barge. He tried to rekindle the civil war in favour of the Commonwealth but was recaptured on 22nd April at Daventry by Colonel Richard Ingoldsby, a regicide, who hoped to win a pardon by handing Lambert over to the new regime. This time he was sent to the Tower, then to Guernsey and finally to Drake's Island in Plymouth Sound.

1671 One of the few people who broke in rather than made an escape, Colonel Thomas Blood and his gang, entered the Tower, somehow talked their way into the treasure room, roughed up the jewel master and made off with a golden orb, sceptre and St Edward's Crown. Fortunately for the guards, Blood and co were captured before they could flee. Oddly, the gang were later given a Royal Pardon by King Charles II and Blood himself was even granted some land in Ireland.

1716 The Earl of Nithsdale was awaiting execution for his part in the Jacobite rebellion of 1715 when he managed a daring escape from right under the noses of his guards. Lady Nithsdale paid a visit to her husband together with two friends a Mrs Mills and a Mrs Morgan. The three dressed the earl in women's clothes, topped his head with an artificial headdress and plastered his face with so much makeup it somehow disguised his long beard. The ladies confused the guards with their comings and goings, hiding their faces in handkerchiefs, so the earl was able to walk out of his cell without anyone suspecting this woman was actually a man.

1942 Two Scots Guardsmen called Fleming and Colvin made their escape by picking a lock with a fork and then lowering themselves into the moat with a rope made from blankets. They crossed the barbed wire barricade by laying down mattresses. Unfortunately for them, they were soon recaptured.

Sources: the londonist.com
The Greatest Traitor by Ian Mortimer