Kammala wannan jumla: A Wasannin Olympics na 2012 a London, Halsall ya yi gasa a wasanni biyar. Halsall ta kai wasan kusa da na karshe na mita 100 na malam buɗe ido, inda ta yi sa'a na 58.52, wanda ya fi kyau a lokacinta na 57.56 da aka kafa a watan Maris. Halsall ya kai wasan karshe na tseren mita 100 na 'yanci kuma
50m freestyle, kammala 6th da 5th bi da bi. A cikin tseren tseren mita 4 × 100 Halsall ya yi iyo a mataki na biyu a cikin kashi 53.29, yana taimaka wa tawagar Burtaniya ta kammala a matsayi na 5. A wasan karshe na 4 × 100 m medley relay da Birtaniya tawagar gama 8th, tare da Halsall samar da wani anga kafa na 54.08.