Sri Lanka’s resistance began on Saturday and continued into Sunday as Thirimanne made an impressive century.
He lost nightwatchman Lasith Embuldeniya, caught at short cover off Dom Bess, in the day’s second over, but settled into a strong partnership of 52 with Angelo Mathews.
Bess and Jack Leach, England’s frontline spinners, continued to bowl too short and tended to follow good balls with bad ones. Root even turned to debutant Dan Lawrence’s funky part-timers, and he beat Thirimanne all ends up.
Thirimanne, appropriately, reached his ton with a cut off a Bess short ball. That was his 11th four from his 226th ball, and brought him his second Test century, with the first coming against Bangladesh in March 2013.
England took the new ball immediately and Sam Curran, as he so often seems to, struck when he was most needed. A little nip backer took Thirimanne’s inside edge and Jos Buttler took a fine catch.
Mathews made it to lunch with captain Dinesh Chandimal as Sri Lanka approached parity.