two years prior"; he disregarded the song as a quick way for her to stay relevant "so nobody forgot her". Graeme Virtue of the Sunday Herald described its sound as "quite melancholy", but praised the song for its catchiness. Tom Ewing from the e-zine Freaky Trigger was mixed on the track. He characterized the song as a "well-performed, pleasant AOR with a sensible heart, Sheryl Crow drawn by Posy Simmonds", but founded it uninteresting, calling the instrumentation "grim" and the production "soggy". Conversely, Cameron Adams of the Herald Sun enjoyed the use of guitars in the instrumentation, calling the song a "great pop tune". Billboard critic Jon O'Brien ranked "What Took You So Long?" third on the magazine's 2018 list of "The Spice Girls' 20 Best Solo Singles"; he called it "one of the simplest" solo Spice Girls singles and considered the production to be "tailor-made for drive-time radio". Lauren Murphy placed it second on Entertainment.ies 2019 list of "The 10 best Spice Girls solo songs". She enjoyed the song's melody and Bunton's vocals, describing it as "a wistful little pop tune", and she considered the song "stood the test of time". Commercial performance "What Took You So Long?" debuted at the top of the UK Singles Chart, with sales of 76,000 copies. This made Bunton the fourth member of the Spice Girls to top the chart as a solo artist, and also set a record for the group, as they became the act with the most individual members to have their own number one single in the country. It spent two weeks at number one, three weeks inside the top 10, nine weeks in the top 40, and 13 weeks on the chart in total, ending at the 41th position on the 2001 year-end chart. The song was certified silver by the British Phonographic Industry (BPI) in the UK in April 2001. As of January 2021, it has sold 295,000 copies in the country. "What Took You So Long?" was moderately successful in the rest of Europe. It reached number six on the Eurochart Hot 100, peaked inside the top 10 in the singles chart of Denmark, Ireland, Italy, Portugal, and Romania, and inside the top 20 in Spain and Sweden. The song performed better on radio across the continent, reaching the third position of the European Radio Top 50 chart, topping the airplay chart in Italy, peaking inside