'The Granatoid Tanks' by Alan Fennell

For the last six months, two scientists have been staying on Planet 73 in order to determine the glass-covered world’s suitability for habitation. Having decided to give the go ahead, the two men contact Space City to arrange to be picked up; the crew of Fireball XL5 are assigned the mission, but Steve and Matt decide to leave the following day as they are preparing a birthday surprise for Venus. However, Planet 73 is far from deserted: as the two scientists find themselves under attack from six Granatoid tanks, they realise that XL5 can never arrive in time to save them…

Paul Maxwell (Colonel Steve Zodiac), Sylvia Anderson (Doctor Venus / Mrs Doughty), David Graham (Professor Matt Matic / Lieutenant 90 / Zoony the Lazoon / Doctor Baker), John Bluthal (Commander Zero / Doctor Simpson), Gerry Anderson (Robert the Robot / Granatoid 1)

Directed by Alan Patillo
Produced by Gerry Anderson
Associate Producer Reg Hill

TX (UK - ITV):
16th September 1963

Notes:
*Featuring Colonel Steve Zodiac, Venus, Professor Matt Matic, Commander Zero, Lieutenant 90 and Robert the Robot