Alsatia in London, was the name given to an area lying north of the River Thames covered by the Carmelites/Whitefriars monastery, to the south of the west end of Fleet Street and adjacent to the Temple. Between the fifteenth and seventeenth centuries it had the privilege of a sanctuary, except against a writ of the Lord Chief Justice or of the Lords of the Privy Council; and as a result it was the refuge of the perpetrators of every grade of crime, debauchery, and offence against the laws. The execution of a warrant there, if at any time practicable, was attended with great danger, as all united in a maintenance in common of the immunity of the place. It was one of the last places of sanctuary used in England, abolished by Act of Parliament named The Escape from Prison Act in 1697 and a further Act in 1723. Eleven other places in London were named in the Acts (The Minories, The Mint, Salisbury Court, Whitefriars, Fulwoods Rents, Mitre Court, Baldwins Gardens, The Savoy, The Clink, Deadmans Place, Montague Close, and Stepney).
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A blog on Alsatia is 
See also Liberties of London