Anne Logie, Historical Environment Volunteer, wrote in 2017 about Cranford Lock-Up (built circa 1838) which is on Historic England's Heritage At Risk register:

A curious conical building stands beside the High Street in Cranford, close to its intersection with Bath Road.  On the damp weekday morning when I visited there were not many people about.  The first person I spoke to knew nothing about the building, but the second, an elderly man, said it was a prison, very, very, old - Victorian.  He said that when he first came to live in Cranford he had wondered about it and asked various people and eventually met an old man, who had lived in Cranford all his life, who told him what it was.

 

Technically, the building is a lock-up rather than a prison.  Built in 1838, too late to house any Hounslow Heath highwayman, the building was intended for drunks and vagrants, though the odd footpad may have been held there. (The local almshouse had been demolished in 1836, necessitating the eviction of its four inhabitants, which probably didn’t help with local homelessness.) According to A History of the County of Middlesex: Volume 3, edited by Susan Reynolds (1962), the lock-up was later used by the parish council as a mortuary.  It would be interesting to know more about such a surprising change of use.
 

The siting of the building is odd.  Its door is at right angles to the road and its single window faces away from it.  Perhaps the lock-up once stood in relationship to some other building, now gone, which would explain its orientation, but in the earliest picture I’ve seen it stands in isolation, with only the backs of some houses, possibly in what is now The Avenue, visible in the distance across an open space.  In later pictures it appears like some bizarre gazebo, gradually being swamped by vegetation.  
 

Known both as Cranford Roundhouse and as Cranford Lock-up, the building was given Grade II listing by English Heritage in 1973.  Unfortunately as it approaches its one hundred and eightieth year the lock-up is in critical need of repair.  The sturdy door appears to have held up well, but the bars are being lost from the window, the roof is badly cracked, and with missing pointing the bricks of the walls are starting to shift.  It would be a shame to lose this little building, the only one of its type in the whole of the London area.  Were it to be restored there is enough adjacent space for some sort of board or plaque to be put up explaining not only the building but its place in the social history of the area.  Cranford, once described as the prettiest village in Middlesex, has been fragmented by arterial roads and boundary changes, and the famous heathland which surrounded it has almost entirely disappeared, though some feeling of what it might once of been is present in nearby Avenue Park.   Preserving the lock up and providing a plaque would contribute to keeping the village’s history visible, and the curious would no longer be dependent upon chance encounters with elderly Cranford residents.  

 The best public transport for the Roundhouse is either the 111 bus, which includes both Heathrow Central and Hounslow East stations on its route, or the 105, which runs from Greenford and passes Southall station. Get off at The Avenue stop in Cranford.  (While there do pause to look at the wonderfully whimsical French chateau style architecture of the buildings around the intersection of The Avenue and Bath Road.  The north west corner is now just houses, and the important looking building in the north west corner, formerly the Berkeley Hotel, is now simply a facade, the interior having been scooped out by the new hotel next to it, but the south east and south west quadrants of shops and flats are still intact, with their turrets, their mock medieval doors, and in at least one case, the original shop ceilings. This fantasia was built in 1934 and commemorates in various details the crest and motto the Berkeley family, who owned most of the local land.)
 

The more adventurous may wish to walk or cycle the River Crane Walk part of which is on Section 10 of the London Loop.  An Ordnance Survey map is recommended.  My impulsive attempt to walk to Hounslow Heath with a only a mobile and a bus map of north west London for guidance had to be abandoned at the Great South West Road.

 

 

All the pictures on this page are by Anne Logie. Follow the highlighted links below to other published images.

The oldest picture I’ve been able to find, published on Maxwell Hamilton's flickr page.  The people must have been quite short.  Note that the side of the lock-up is being used as a parish noticeboard. 
 

There are two pictures in the Metropolitan Museum collection  dated 1967.  Cranford Round House image one. Cranford Round House image two. The estate has not yet been built.  The hedge of the earlier pictures has been replaced by a wall and an iron gate through which vegetation, probably ivy, is growing.  Ivy is attacking the roof.
  

Current (February 2017) state of repair:-

 

 

Below is the fine restoration achieved in 2017:

Hounslow Council and Heritage of London Trust have worked together to restore the building, and have provided an interpretation panel so the lock-up’s place in the history of the community will be clear to all.  The restored building was unveiled on 6 December 2017.  More about the restoration can be found at https://www.hounslow.gov.uk/news/article/356/history_unlocked_in_cranford . 

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Postscript: The Londonist published an inspiring piece about the re-opened Lock-Up used in history lessons for children!