Mill’s ancestors held land in Greatham, on the River Arun, about five miles from Arundel, in the fourteenth century.
In 1624 Mill contested Arundel against the earl of Arundel’s candidate, Sir George Chaworth*. A formal poll showed a slight advantage to Mill, but the mayor kept the meeting open until more voters could be found for Chaworth, whom he then returned. Mill’s supporters petitioned the Commons to have the election overturned and the privileges committee found in their favour. Consequently on 24 Mar. the Commons ordered the mayor to make a new return electing Mill.
Early in 1625 Mill was marked as ill in the records of Sussex Lent assizes, when he was fined £20 for having committed a man to gaol without taking an examination.
Mill’s second wife died in January 1626 and Arundel’s steward, John Peers, hoped that this fact, together with his continued ill health, would deter Mill from seeking re-election, leaving space for Nicholas Jordan. On 16 Jan. Peers reported that although Mill had ‘complimentally said he would thank them to spare him, and that he desired it not’, he had also refused to inform the borough of his lack of interest and was ‘resolved to serve if he be chosen’. Peers therefore recruited Sir Thomas Bishopp*, an important Sussex magistrate, to persuade Mill not to stand. Bishopp, however, proved unsuccessful and, despite being removed from the commission of the peace at about the same time, Mill was re-elected.
Restored to the bench by the following October, Mill also acted as collector of billeting expenses in the rape of Arundel. There is no evidence that he sought re-election in 1628; instead he probably supported John Alford*, whom he appointed a trustee and executor of his will, which he drew up when he was ‘sick in body’ on 10 Sept. 1629. In this he asked to be buried in the family chapel in Pulborough, a nearby parish church, and named as a trustee and executor the rector, Laurence Pay, an ally of Richard Montagu, the anti-Calvinist bishop of Chichester. He also bequeathed 2s. to Chichester Cathedral. He had already settled the greater part of his estate on his eldest son, and provided for two married daughters, but he left portions totalling £2,900 to his ten remaining children.
