Returning to the Moonbase, the Doctor confronts Slaar and the remaining Ice Warriors and must find a way of deflecting the invasion fleet that is heading towards them.

Sarah has been caught by the Sontaran, Field Major Styre, who is conducting cruel experiments on the captured humans, paving the way for a full-scale invasion.

Junior Laniyan is a English actor and tap dancer. 

>He appeared in the BBC childrens series Bodger and Badger and then enrolled in Sylvia Young Theatre School as a full time student from 1992- 1998 and has since worked on in theatre, Film and television. In 1993 he played the role of Errol alongside Richard Briers and Imelda Staunton in If You See God Tell Him, also for the BBC. In 1997 he worked again with Richard Briers in the acclaimed period drama A Respectable Trade where he played the part of Matthew. 

Junior Laniyan is well known for playing Benji McHugh in Family Affairs but has also played Ric Griffin's medical student son Leo Griffin played by Hugh Quarshie in a number of episodes of the BBC's Holby City, womanizing football player Stuart in in the popular UK soap Coronation Street and in 2001 played Pvt. Bell in Danny Boyle's Movie 28 Days Later.

As well as acting, Junior Laniyan is also one of the UK's most preeminent tap practitioners. He is well known for performing with Robbie Williams in the number Mr Bojangles for Robbie Williams Live at the Albert Hall. He has also danced on stage at London's Queen Elizabeth Hall, Cochrane Theatre, Purcell Room, Royal Festival Hall and Hackney Empire among other theatres and regularly performs and teaches throughout Europe. He founded and is the host of the the UK's first regular tap dance Jam session, The London Tap Jam based in London's Ronnie Scott's bar.

Sean Gilder is an English stage, film and screen actor, he is also a playwright.

Gilder was born in Brampton, Cumbria, England. He is best known for his portrayal of Paddy Maguire on Shameless from 2005 to 2010, and as Styles on Hornblower. 

He has appeared in Doctor Who (as the Sycorax Leader) as well as New Tricks, Gangs of New York, and the 2004 film, King Arthur, which starred Keira Knightley and Ray Winstone. 

Jim Francis was one of the visual effects designers on the Doctor Who story The Caves of Androzani. 

He was a major force in British television special effects during the 1980s and 1990s. He served as VED on The Hitchhiker's Guide to the Galaxy, most of Blake's 7 and the eighth season of Red Dwarf. He worked, or at least was credited, up to the year of his death.

Designer for the stage play Doctor Who and the Daleks in Seven Keys To Doomsday

Napier has designed for the National Theatre, notably the production of Peter Shaffer's Equus, Trelawny of the Wells, An Enemy of the People and Candide. He has also designed for the Royal Opera House, for Glyndebourne, for the English National Opera and others. He designed Children of Eden, Who's Afraid of Virginia Woolf? and Jesus Christ Superstar in London's West End. 

In the United States, in addition to numerous Broadway productions, he designed and co-directed the show for illusionists Siegfried & Roy at The Mirage, Las Vegas. He also designed the Captain EO video starring Michael Jackson for Disney and the Steven Spielberg film Hook.

Napier's design awards include the Laurence Olivier Award for Best Set Design for King Lear, Lohengrin, and Burning Blue. Napier has won Tony Awards for Nicholas Nickleby, Cats, Starlight Express, Les Misérables and Sunset Boulevard.

He won the 1987 Drama Desk Award for Outstanding Set Design for Starlight Express and Les Misérables and has twice won the Drama Desk Award for Outstanding Costume Design for Cats in 1983 and Starlight Express in 1987. He has won The Critics' Circle Award for set design twice, first in 1989 for Miss Saigon and again in 1997 for Peter Pan.

Neville Barber played Dr. Humphrey Cook in the Doctor Who serial The Time Monster and Howard Baker in A Girl's Best Friend.

Roger Delgado was an English actor, best known for his role as The Master playing alongside the Third Doctor, Jon Pertwee.

He was born in Whitechapel, in the East End of London within the sound of the Bow Bells. He attended the CVMS, a Roman Catholic secondary school in Holland Park. Delgado worked extensively on the British stage, and on TV, film and radio.

He appeared in the 1955 BBC Television serial Quatermass II, had a role in the Powell and Pressburger wartime drama Battle of the River Plate (1956), and came to wide popular attention in Britain when he played the Spanish envoy Mendoza in the ITC Entertainment series Sir Francis Drake (1961-62). Other work included roles in The Champions (1969), Danger Man (1961), The Saint(1962, 1966), and Randall and Hopkirk (Deceased) (1969). He also appeared in The Avengers (1961, 1969), The Power Game (1966) and Crossfire (1967). In film, he appeared alongside Bing Crosby and Bob Hope in The Road to Hong Kong.

He began work on Doctor Who in late 1970, his first broadcast appearance being in the January 1971 adventure Terror of the Autons and was the principal villain for all of Season Eight's stories. He continued to make appearances in both Seasons Nine and Ten, his last being in the story Frontier In Space.

Delgado planned to leave the series in 1974 and a grand battle was planned between the third Doctor and the Master which would end in the Master's death and the Doctor's regeneration. However, whilst on location during filming of L'Escadron d'or avec Coluche et Philippe Léotard (the fourth episode of French mini-series La Cloche tibétaine), he was killed in a car crash as his chauffeur-driven vehicle went off the road into a ravine.

de Marney's career in the theatre began in 1923 and continued almost without interruption, taking in film, radio and television parts. He toured with Mrs. Patrick Campbell in The Last of Mrs. Cheyne. In 1930 he played Gustave in The Lady of the Camellias, and toured South Africa as Raleigh in Journey's End. In 1934 he played Tybalt in Romeo and Juliet at the Open Air Theatre, and Giovanni in 'Tis Pity She's a Whore at the Arts.

Thrillers tended to be his stock in trade, appearing in a revival of Sutton Vane's Outward Bound during the 1930s, as well as Agatha Christie's Ten Little Indians, Dear Murderer, as well as a revival of Gerald Du Maurier's Trilby in later years. He also appeared on radio as the Count of Monte Cristo, and was the first actor to portray Leslie Charteris' Simon Templar on radio, when The Saint debuted on Radio Athlone in 1940 for six episodes.

In 1931 he became director of the Connaught Theatre, Worthing, and in 1932, with his brother, the actor Derrick De Marney, he founded the Independent Theatre Club at the Kingsway Theatre, where he directed Emil Ludwig's Versailles and an adaptation of Schnitzler's novel Fraulein Else. He also directed Louis Golding's Magnolia Street Story and Master Crook, originally called Cosh Boy. With his brother he alternated as Slim Callaghan in Meet Slim Callaghan at the Garrick Theatre and carried on the same role in the play's sequel Slim Carves, which he produced and directed.

He also made his film debut in 1931, and went on to appear in a number of quota quickies of the period, including mystery horror films The Unholy Quest (1934) and The Mystery of the Marie Celeste (1935), the latter opposite Bela Lugosi. These roles in the macabre would continue throughout his career and took in films such as The Pharaoh's Curse (1957), Boris Karloff vehicle Die, Monster, Die (1965) and The Hand of Night (1966).

After starring in 'B' movies like Duel Alibi (1948), and No Way Back (1949), he uprooted to Hollywood, where he appeared in a number of famous television series such as Bonanza, Wagon Train, Maverick, and The Twilight Zone. He was a series regular on Johnny Ringo. As well as small roles in films such as The Ten Commandments (1956), and Spartacus (1960). He returned to Britain in the 1960s and continued to appear in television series such as Maigret, Dr. Finlay's Casebook, Doctor Who, and Z-Cars. His last film appearance was in The Strange Affair (1968).

He died in 1971 following an accident on the London Underground.

Actor who appeared in the 1974 story Planet of the Spiders.

Also appeared in Fawlty Towers, Follyfoot, Harriet's Back in Town, The Rivals of Sherlock Holmes, War & Peace, The Protectors, New Scotland Yard, Clinic Exclusive, The Guardians, ITV Sunday Night Theatre, Armchair Theatre, One More Time, Crossplot, Battle of Britain, BBC Play of the Month, Joanna, The Saint, Detective, Softly Softly, Der Rivonia-Prozeß, African Gold, Once Upon a Dream, Jean's Plan 

Lionel Sansby played a passenger in Nightmare of Eden and a Krarg in Shada.

Also appeared in The Home Front, Funny Man, Armchair Thriller, Blakes 7, Villains, Doomwatch