Next month will be the 40th anniversary of everyone's favourite robot dog, K9, since his first appearance on our TV screens in the Doctor Who story The Invisible Enemy. And we're celebrating!

Many fans have loved hearing the cries and witty repartee of K9 voiced by John Leeson since his first appearance and travels with the Fourth Doctor, Tom Baker. From the multiple K9s who travelled the universe, Mark One stayed with Leela on Gallifrey after The Invasion of Time, Mark Two kept travelling with Romana II in E-Space after Warrior’s Gate, Mark Three was a gift to Sarah Jane Smith in the Doctor Who spin off show K9 and Company, and Mark Four replaced Mark Three after he’d sacrificed himself to save the Tenth Doctor, Sarah Jane Smith, Rose and the world from the Krillitanes in the Doctor Who TV episode School Reunion.

To celebrate K9’s 40th anniversary, Big Finish has some special offers on releases that feature the robo-canine companion. To take advantage of these special offers, go to page https://www.bigfinish.com/offers/v/k940 and use offer code marius to access them. Offers will run until 23:59 UK time on Monday 25th September.

K9 first encountered the Doctor when he was trying to defeat the Swarm in The Invisible Enemy almost 40 years ago. And in 2014, the Swarm returned to fight the Seventh Doctor, Ace and Hex in Revenge of the Swarm.

The Doctor thought he had defeated the microscopic Nucleus of the Swarm in his fourth incarnation. He was wrong. It survived within the TARDIS, and now it has brought it back to Titan Base, back to the point of its own creation. It has a plan that spans centuries, a plan which will result in the Nucleus becoming more powerful – and larger – than ever before. To defeat it, the Doctor, Ace and Hex must confront the Nucleus within its new domain – the computer-world of the Hypernet, the information network crucial to the survival of the human empire. But if the Doctor is to save the day, he has to risk everything and everyone he holds dear...

Get this adventure for £6 on CD or £5 on download.

K9 also features in a number of Big Finish’s novel adaptations. Created in the days between the classic and current series of Doctor Who, Virgin Publishing released numerous Doctor Who novels, some of which have been made into full-cast audio dramas by Big Finish. The Well-Mannered War, The English Way of Death and The Romance of Crime are available for £6 on CD or £5 on download each.

You can also get these adventures in limited edition box sets. Volume 1 contains The English Way of Death and The Romance of Crime, and Volume 2 combines The Well-Mannered War with Seventh Doctor adventure Damaged Goods by Russell T Davies. These limited edition box sets are available at £25 on CD or £20 on download.

In The Companion Chronicles series, K9 stars in The Beautiful People with Lalla Ward (available on CD at £4.50) and The Time Vampire with Louise Jameson (available on CD at £4.50 or download at £3.99). Or you can get Big Finish’s version of Shada, the lost Doctor Who story by Douglas Adams, starring Paul McGann, Lalla Ward and John Leeson as K9 for just £3.50 on CD.

K9 rejoins Tom Baker in several of the Fourth Doctor Adventures with the late Mary Tamm as Romana and Louise Jameson as Leela. Make sure you check out the offers page to fill any missing spaces in your collection!

Fans of Gallifrey will be pleased to know that they can also add to their collections! For those who have yet to hear it, Gallifrey consists of popular tales of intrigue and political manoeuvring from the seat of Time Lord power. Join Romana, Leela and K9 as they find enemies on all sides in a delicate game with the fate of Gallifrey hanging in the balance. The early stories of Gallifrey are all available at £4 on CD, or you can get Series 4 and/or Series 6 (both starring K9) for £20 on CD or £18 on download.

Gallifrey releases are also available in a bundle – get Series 1 on CD for £16, Series 2 and 3 for £20 each, or all the adventures from the first three series for £50.

To access these special offers, go to page https://www.bigfinish.com/offers/v/k940 and use offer code marius to access them. These offers will run until 23:59 UK time on Monday 25th September. Affirmative!