Beginning in 1999, Big Finish Productions, under licence from the BBC, began a range of audio plays on compact disc, with one released every month starring one of the surviving actors to play the Doctor, namely the Fifth, Sixth and Seventh Doctors, with the Eighth Doctor following them in 2001. The Doctors are frequently joined in the audio plays by companions from the television series and new companions created for the audio range. Stories in the ongoing Eighth Doctor series were originally released in "seasons" of between four and six consecutive releases, but this pattern ceased after "Doctor Who" returned to television in 2005. In 2009, Tom Baker agreed to appear in five new audio stories for the BBC called "Hornets' Nest". A second five-CD series, "Demon Quest", followed in 2010, and the series "Serpent Crest" followed that in 2011. Also in 2011, Baker began appearing in audio plays as the Fourth Doctor for Big Finish, starting with "The Fourth Doctor Boxset", a box set containing the "lost stories" submitted during Baker's time on television, "The Foe from the Future" and "The Valley of Death". CD box sets featuring the War Doctor were released between 2015 and shortly after John Hurt's death in 2017, and audio releases with the Tenth Doctor began from 2016.