During the Siege of Colchester the following was noted in A Diary of the Siege of Colchester:
"Wednesday 28th June 1648 - Chewed and poisoned bullets taken from several of the besieged. Affidavit made by those soldiers of the besieged who brought them out of Colchester, that they were given out by the Lord Goring's special command. These examinations were sent to the Lord Goring with this message from our General - that his men should expect no quarter hereafter if they used such bullets...
>From the Firth & Davis' Regimental History of Cromwell's Army, Vol. II, p.573; The Tower Guards, the following is found concerning the siege and poisoned bullets:
Wednesday 5th July 1648 - The Drakes [type of cannon] recovered, and our former ground also; Lt-Col. Weston, Lt-Col. Weeks and 80-odd prisoners were taken, most of them sore cut for shooting poisoned bullets (20 of them died the next day). Of our part, we had slain Lt-Col. Shambrooke and some others of Col. Needham's regiment who were engaged."
"Needham's successor was Lt-Col. William Shambrook, who fell on July 5th. It was alleged that both Needham and Shambrook had been shot with poisoned bullets or 'chewed bullets rolled in sand', and the Royalist Generals admitted using 'rough cast slugs'. At the subsequent trial of the Earl of Norwich (Lord Goring) in 1649 evidence was given on this charge."
It should be noted that the above statements concerning poisoned bullets, whether presumed or real, would probably explain the harsh measures imposed on the besieged Royalist after they had surrendered to Sir Thomas Fairfax.