On 7 March 1643, Parliament issued orders for the fortification of London.
After the indecisive Battle of Edgehill in October 1642, the King had marched slowly towards London, allowing the outmanoeuvred Parliamentarian commander, the Earl of Essex, to once again get between him and the capital. At Turnham Green on 13 November 1642, the two armies faced off against each other – the King unwilling to risk an attack against a larger Parliamentarian army and Essex wary of using his inexperienced troops. Despite desultory artillery fire, neither side fully engaged and Charles and his army were forced to retreat to Oxford for the winter.
Turnham Green was a terrifying wake-up call for the men behind Parliament’s war effort. With Oxford just 60 miles away, London remained vulnerable and the city scrambled to protect itself.
Following a survey of these defences by Alderman Randall Mainwaring, a proposal was put to the Court of Common Council – the City of London’s government – and then ratified by Parliament on 7 March 1643 for the “Order for intrenching and fortifying the City of London”. Over the next year a massive series of earthworks and defences were thrown up around the city.
Antiquarian George Vertue’s 1738 plan of the London Lines of Communication
‘The Lines of Communication’, as they were known, were initially made up of street barricades, blocking streets with barriers or chains, the building of guardhouses and small earthworks by main roads. But in 1643 a major construction effort was made to provide a comprehensive ring of fortifications around the city, creating one of the largest urban defence systems in Europe.
Much of the work was done by volunteer labour, organized by the city’s militia – the ‘Trained Bands’ who already formed a major part of the Earl of Essex’s army – and the livery companies, which were the descendents of the city’s medieval trade guilds. Up to 20,000 people – including men, women and children – are thought to be involved and the works were completed in under two months, finishing in mid-May.
Thought to have been designed by Dutch siege engineers (the Dutch were experts at major defensive works thanks to their on-going wars against the Spanish), this continuous earthen rampart with 23 forts, redoubts, and sconces surrounded London at a distance of one and a half to two miles from the city centre.
Although the Royalists never again approached or even attacked London, the fortifications failed their only test when the New Model Army easily entered London in 1647. They were levelled by Parliament the same year and although evidence of their existence remained for many years, the constant expansion and rebuilding of London over the centuries means that they are now lost.
You can read Parliament’s original oder from 7 March 1643 at Wikisource, there is a fascinating article that goes into much details about the location, size, and shape of the defences at Fortified Places and you can even take a walk along the line of the defences north of the River Thames thanks to this handy map from The Londonist.