Irby came from a family of lawyers based in Lincolnshire. His grandfather was appointed clerk of the peace for Kesteven in 1510, and his uncle Leonard began the family parliamentary record by sitting for Stamford in 1545, subsequently representing Boston in eight Parliaments. By 1552 Irby’s father had acquired Whaplode, 12 miles south of Boston, and Irby himself expanded the estate.
In the opening session of the first Stuart Parliament Irby was appointed to seven legislative committees, including those to empower justices of the peace to release debtors from gaol (31 Mar. 1604), to preserve pheasants (25 Apr.), to secure the rights of creditors in cases of parliamentary privilege (26 Apr.), and to abolish benefit of clergy in cases of stabbing (4 May). He was named to consider three measures of local import, for the recovery of drowned lands in the fens (12 May), the exchange of property between Sir Thomas Monson* and Trinity College, Cambridge (26 May), and he took the chair on the bill for the relief of the Norfolk recusant Thomas Lovell, which he reported on 4 July.
In the second session he was appointed to committees on the bills for the better satisfying of due debts (20 Mar. 1606) and to confirm the abolition of sanctuary (20 May).
Perhaps having been dissuaded from proceeding by bill, Boston’s corporation petitioned the Lincolnshire sewers commissioners in the summer of 1609 for help in controlling the River Witham. Irby demanded that the costs of repairing the sluices should be shared by the whole level which benefited from it, but his proposals failed to gain the support of the 2nd earl of Lincoln (Henry Clinton†). He also made a stand against the activities of Crown agents, William Tipper and Robert Dawe, concerning titles to land reclaimed from the sea, asserting that all rights of ownership and common already belonged to the inhabitant landowners and commoners.
At the opening of the fourth session of the first Jacobean Parliament, on 9 Feb. 1610, Irby was nominated to the committee for privileges and returns. His other appointments during the session concerned bills against forcible entry (24 Feb.), warrants of attorney (29 Mar.) and to prevent elopement (8 May).
Irby and his Lincoln’s Inn colleague Leonard Bawtree* represented Boston in the 1614 Parliament and were granted £30 by the corporation towards the cost of obtaining statutory confirmation of the town’s charters.
On the death of the earl of Exeter in 1623 Irby succeeded as Boston’s recorder, but resigned from the aldermanry, and requested licence to absent himself from the town for six months, presumably on business.
