[4] In July Sydenham defeated a plundering party from the garrison of Wareham at Dorchester, and hanged six or eight of his prisoners as being "mere Irish rebels".
[7] He also defeated Sir Lewis Dyve, the commander-in-chief of the Dorset Royalists, in various skirmishes, in one of which he killed, with his own hand, Major Williams, whom he accused of the murder of his mother.
[8] In February 1645 Sir Lewis Dyve surprised Weymouth, but Sydenham and the garrison of Melcombe Regis succeeded in regaining it a fortnight later.
[18] Sydenham sat for Dorset in the parliaments of 1654 and 1656, distinguishing himself during the debates of the latter by his opposition to the exorbitant punishment the house wished to inflict on James Naylor.
[19] When the Protector's intervention on behalf of Naylor raised a complaint of breach of privilege, Sydenham recalled the house to the real question.
[21] When in December 1657 Sydenham was summoned to Cromwell's House of Lords, a republican pamphlet remarked that, though "he hath not been thorough-paced for tyranny in time of parliaments", it was hoped he might yet be "so redeemed as never to halt or stand off for the future against the Protector's interest".
[26] Sydenham attempted to justify the violence of the army to the Council of State, "undertaking to prove that they were necessitated to make use of this last remedy by a particular call of divine Providence".
[28] At the restoration the Act of Indemnity and Oblivion included him among the eighteen persons perpetually incapacitated from holding any office on 29 August 1660, and he was also obliged to enter into a bond not to disturb the peace of the kingdom.