Jessica won two AAA U15 titles and the English Schools junior high jump in 2000 and was second in the English Schools Inters high jump and heptathlon. She missed the British U15 record for heptathlon by just 14 points finishing in second place in a junior international in Switzerland. At U17 level she won the AAA high jump in 2001, with a best that year of 1.75 and in 2002 she won the English Schools Inters high jump with 1.80.

In 2003 Jessica won the AAA indoor pentathlon and outdoors won the Northern Junior high jump and AAA Junior 100mh. The World Youth Championships saw her finish in fifth place with 5311 points.

In 2004 she led the World Juniors Championships having achieved a pb of 13.57 for 100m hurdles, and although she finished 8th she added 178 points to the 5364 pb she had set earlier in the year. She ended 2004 with silver medals at 100m hurdles and high jump at the Commonwealth Youth Games and made further progress by winning the 2005 AAA Indoor pentathlon. In this competition she set pbs in five of the seven events, including 1.85 for high jump.

She then set UK junior records for heptathlon at both her championships events: taking gold at the European Junior Championships and bronze at the World University Games.
In 2005 she was ranked amongst the best world juniors at heptathlon and was ranked second at the100m hurdles and 11th at high jump.

2006 was another year of great achievements with her first senior medal, a bonze medal at the Commonwealth Games in Melbourne. In amassing a score of 6269pts she set four personal bests.
At the European Championships in Gothenberg, Jessica finished in eighth place, just 3 points behind Kelly Sotherton, and set personal bests in the shot putt and 200m.
 

1.95
National Record