Execution Dock

Execution Dock was used for more than 400 years in London to execute pirates, smugglers and mutineers who had been sentenced to death by Admiralty courts. The "dock", which consisted of a scaffold for hanging, was located near the shoreline of the River Thames at Wapping. Its last executions were in 1830.

The legal jurisdiction for the British Admiralty was for all crimes committed at sea. The dock symbolised that jurisdiction by being located just beyond the low-tide mark in the river. Anybody who had committed crimes on the seas, either in home waters or abroad, would eventually be brought back to London and tried by the High Court of the Admiralty .

Capital punishment was applied to acts of mutiny that resulted in death, for murders on the High Seas and specific violations of the Articles of War governing the behaviour of naval sailors, including sodomy. Those sentenced to death were usually brought to Execution Dock from Marshalsea Prison (although some were also transported from the Newgate). The condemned were paraded across London Bridge past the Tower of London. The procession was led by the High Court Marshal on horseback (or his deputy). He carried a silver oar that represented the authority of the Admiralty. Prisoners were transported in a cart to Wapping; with them was a chaplain who encouraged them to confess their sins. Just like the execution procession to Tyburn, condemned prisoners were allowed to drink a quart of ale at a public house on the way to the gallows. An execution at the dock usually meant that crowds lined the river's banks or chartered boats moored in the Thames to get a better view of the hangings. Executions were conducted by the hangmen who worked at either Tyburn and Newgate Prison.

...
Wikipedia