Twell's personal best time for the 1500 metres is 4:02.70, set in
Barcelona, Spain on 1 August 2010. She competed in the women's 1500 metres at the
2008 Beijing Olympics and was eliminated in her heats running 4:06.68. In September 2008, Twell was named
European Athletics Rising Star of 2008. In January 2009 she was named "Telegraph Ten for 2012" – 10 of Britain's brightest young sports stars in
The Daily Telegraph. She began the 2009 cross country season well, winning at the
Antrim International Cross Country. A few months later, Twell finished 38th in the
2009 World Cross Country Championships in Jordan. Although she was the fastest Briton in the race, she was disappointed with her performance and stated that she resolved to do better in the next championships. She set a new personal best in the
5000 metres in May 2009, winning the Artur Takac Memorial in 15:18.47 – a meeting record. She had a disappointing run at the
2009 European Team Championships over 3000 m, finishing in fourth in a time well outside her PB. At the
2009 World Championships she was never in contention in her heat at 1500 m and then when one of the favourites she was only 11th in the European Cross Country Championships (under 23 race). Her 2010 was marked by improvements in her personal bests on the track. She set a
1500 metres best at the
Weltklasse Zurich Diamond League meeting, finishing third and ahead of
Lisa Dobriskey with a time of 4:02.54. Stepping up to the 5000 m at the
Memorial van Damme in Brussels, she smashed her previous best by 22 seconds to set a new
Scottish record of 14.54.08, breaking
Yvonne Murray's 15-year-old mark. She ran at the
Women's 5K Challenge in London in August 2010 and took third place behind
Sylvia Kibet and
Linet Masai. Reflecting on the race, she said: "To run 15:32 is great for me and third was just what I aimed for." Twell suffered a fractured ankle competing in a cross-country race in Belgium in February 2011. A further foot injury in June 2012 ended her hopes of competing at the
2012 Summer Olympics. Twell won the
London 10,000 in 2018 and 2019. == Competition record ==