He was taken to the hospital where he was seen by a doctor, then discharged with advice to rest. His co-star, Imelda Staunton, who was also feeling unwell, did not appear at the evening performance on April 2.

Neither will appear on April 3. They will be replaced by their understudies Fergus March and Sharon Eckman respectively.

According to an April 3 press statement, "Mathew Horne and Imelda Staunton were both taken ill during the matinee performance yesterday. Both were seen by doctors later that day and have been told they have a virus. As a consequence at this evening's performance the role of Sloane will be taken by Fergus March and Kath by Sharon Eckman. At this stage it has not yet been confirmed whether Mathew Horne and/or Imelda Staunton will be back on stage tomorrow. The decision will be taken tomorrow morning."

March's West End theatre credits include playing Sky in Mamma Mia! and appearing in We Happy Few. Eckman's West End credits include A Funny Thing Happened on the Way to the Forum and Critical Mass at the Almeida.

The production is scheduled to run for one more week only, through April 11.