View London's English Civil War defences 1642-3 in a larger map.
"And it was also Ordered that there should be Bulworkes presently raised in the Fields before the Citty, to Fortifie the same against any Invation ..."
A Continuation of Certain Speciall and Remarkable Passages
24 October 1642
Fear that the king and his army were marching on London in October 1642 sent the capital scrambling to fortify itself. The start of November saw the city digging defensive positions, with more forts, ramparts and ditches completing the ring of defences over the following year.
Click on the map markers above to see the conjectural positions of the fortifications (view in larger window) ...
The quotation above, taken from a report written only a day after the Battle of Edgehill - records a committee on the order of Parliament instructing hundreds of men to raise bulwarks in what is now St Pancras and Hyde Park.
Other fortified positions followed in areas such as Piccadilly, Holloway Road and Whitechapel, with outposts in places like Islington and Mile End guarding major approach routes. The undertaking by the Trained Bands and the city's inhabitants was evidently huge, though the strength of the defences was never tested: the closest Charles I got to London was Brentford and Turnham Green in November 1642.
Almost no archaeological evidence remains of the 'lines of communication', as the earthworks were known at the time, making the plotting of some of the marker points conjectural (a number of alternative points for some of the positions are shown). No contemporary map is known to exist, though a review by English Heritage draws together a number of 17th century reports and 18th century maps to help identify positions.
David Flintham's article on the fortifications gives more details about their construction (while providing a list of other useful primary and secondary sources), while Stephen Porter and Simon Marsh's The Battle for London (2010) explores them in the context of the capital's 1642-43 militarisation.
Plotting the points brought the defensive ring out at around 11 miles, allowing for the straight lines imposed by the mapping tool. The one visible remainder appears to be in Hyde Park, with the remainder of an earthwork apparently running alongside Park Lane. I'll add it to the map when I get round to taking a photo!
See more interactive maps
A walk around Brentford and Turnham Green