High Quality Content by WIKIPEDIA articles! The Marshalsea was a prison on the south bank of the River Thames in Southwark, now part of London. From the 14th century until it closed in 1842, it housed men under court martial for crimes at sea, including those accused of "unnatural crimes", political figures and intellectuals accused of sedition, and—most famously—London`s debtors, the length of their stay determined largely by the whim of their creditors.