McShane was something of a prodigy, winning the World Under-10 Championship at the age of eight. Shortly afterwards he found a sponsor in the form of computer company Psion. At sixteen he became the youngest ever British grandmaster, gaining the three results required ("grandmaster norms") in tournaments in Germany, Iceland and the Politiken Cup in Copenhagen, Denmark.
Among McShane's more notable results are joint first in the 1998 Bunratty Masters in Ireland with John Nunn, winning five of his six games, and joint winner with Stuart Conquest and Bogdan Lalic of the Iona Tech Masters in Kilkenny. McShane led the 2002 British Championship in Torquay, and was in a good position in the final round before blundering and losing to the tournament's winner, Ramachadran Ramesh. McShane finished tied for fourth.
From around 2002, McShane has been facing stiffer opposition, including players from the world's top ten. He played for England in the 2002 Chess Olympiad in Bled, scoring 6.5/11, and won the silver medal at the World Junior Championship in Goa. In 2003 he finished a respectable fifth in the strong Hrokurinn tournamnet in Reykjavik, finishing ahead of Britain's number one player Michael Adams and drawing games against Viktor Korchnoi and Alexei Shirov. Shortly afterwards, he beat Shirov in a Reykjavik blitz tournament. In the 2003 Siegman tournament in Malmö, he finished third with 5.5/9, drawing his game with the tournament winner, Vasily Ivanchuk. Also in 2003, McShane finished 27th out of 207 with 8/13 in the strong European Individual Championships in Silivri in Turkey, 1.5 points behind the winner, Zurab Azmaiparashvili. Shortly afterwards he tied for first with Alexei Dreev and Krishnan Sasiskiran in the North Sea Cup played in Esbjerg in Denmark with 6.5/9, finished tied for second in the Politiken Cup in Copenhagen with 8.5/11 and won the Malmö Masters with 7.5/9, a point and a half ahead of his nearest rival.
McShane is a strong blitz player (chess played with fast time limits). He won the 136-player Kuppenheim tournament in 2003 ahead of Vladimir Epishin and former German blitz champion, Robert Rabiega, finishing with a score of 50.5/53. In this tournament he played his games over the internet, while all other participants were in the playing hall in Germany. In 2003 he won the British Blitz Championship held at Uxbridge with a score of 14.5/16 and the Greenland Open rapid tournament with 8.5/9.
Later in 2003 McShane was set to enter Oxford University to read philosophy and mathematics, a move likely to result in a decrease in his chess-playing activites. He has continued to play the in German Bundesliga, however, and in December 2003 finished joint first with Miguel Illescas Cordoba and Emil Sutovsky in Pamplona, with a tournament performance rating of 2701.