it rises at the vale of health on hampstead heath, fills hampstead ponds, down through gospel oak and kentish town to king's cross, under the canal (really) southwards through clerkenwell (that's why so many of the streets are sloping) underneath Farringdon road and into the Thames at Blackfriars. you can trace it in the street names - Fleet Street, Turnmill Street, Fleet Road, etc. It was also known as the"holborne" and 'turnmill brook'.
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