According to Cricinfo it's 2023, he moved when he was just past 18.
I know I'll cop some flack, possibly quite a lot, for saying this, and it's been said before but I was thinking that with the current county schedule and pitches it must be hard for any genuine quick bowler growing up in England (who hasn't been messed up by Loughborough) to compete against guys who got to grow up on hard overseas pitches that actually favour that style. Hence they've no hope of gaining experience at first class level and competing with either more experienced overseas / ineligible imported quicks that feature conspicuously in say, Hampshire, or medium pacers who thrive on the damper softer pitches earlier in the season (and 2nd XI is probably too low a standard and worse pitches, so it's trite and useless to say 'bowl better'). That said the last world class genuine quick of any permanence that England produced was Willis, so that's not root the problem by a long shot. Can't help though.
Durham 8/58, might just scrape past their first innings score. I see Dexter only conceded 1 run in his first innings spell.
Speaking of such signings, I see Parnell's gone to Worcs. Whenever I've seen him bowling he's bowled rubbish, even when he's bowled well.