Few places in London have a less appropriate name than Mount Pleasant. For a start this isn't a mountain, or even a mount - it's more a mildly sloping hillside on the banks of the Fleet valley. And, more to the point, it's never been pleasant. Go back far enough and this used to be a dismal boggy marsh - and that's before it was downgraded to a public dungheap. Mmmm. Then in 1794 the authorities decided that this would make the perfect spot for a new jail and so built the Coldbath FieldsPrison, home to more than a thousand unfortunate wrongdoers. Inmates were forced to endure a punishing regime of solitary confinement and hard labour, so harsh that this HouseofCorrection earned a fearsome reputation. When the prison closed in 1877 the Post Office moved in instead, and they slowly transformed the buildings into London's largest parcel and lettersorting office. To remove all trace of the prison's name they also rechristened the area 'MountPleasant' - with more than a hint of sarcasm. The largest station on the Post Office underground railway (or 'Mail Rail') opened here in 1927, roughly halfway between the termini at Paddington and Whitechapel. I was fortunate enough to visit Mount Pleasant when I was a kid back in the 1970s. It was incredible to descend into the bowels of the sorting office to find a miniature train set in operation, and watching driverless engines pulling carriages full of mailbags disappearing into tiny tunnels. Mail Rail closed down a couple of years back - it was far too expensive to run - but the monolithic sorting office is still there, its fleet of bright red vans parked high above the Fleet below. And, if you join the posties sipping beer across the road outside the AppleTree pub, these days it's almost pleasant. Following the Fleet: To see where the Fleet once flowed between King's Cross and Farringdon, look on a current map and trace the boundary between the boroughs of Camden and Islington