The Mega (Big Finish)

If The Mega had been made in 1971, it could have been a classic season finale. There are so many strong Pertwee-era ingredients that it feels perfectly at home in Season Eight, the only thing missing is the presence of the Master. Here, it's lovingly nursed from a storyline by The Web Planet writer Bill Strutton by Simon Guerrier, and performed by Katy Manning and Richard Franklin.

The Mega deals with an attempt to force the West to disarm and put an end to war by Prince Cassie of the fictional nation Golbostan, backed by the alien Mega - beings of pure energy. The story begins with the Doctor, Jo, and Captain Yates heading through a sea of protesting youngsters to a demonstration of a horrific new weapon - a nerve gas which can choose its victims. A regular army General comments that the gas can be used on the protestors, much to the Doctor's outrage - at which point the General is assassinated by the Mega, and things begin to unravel. The Doctor and Jo are led to Cassie's castle in Golbostan by the Mega, whilst things get worse - the Prime Minister is the next target, live on TV, the Brigadier is placed under arrest, and Yates and Benton try to keep order when panic-stricken rioting breaks out amongst the public.

The story resonates with both period and modern concerns about war, protest, and the use of WMDs, and given Malcolm Hulke-like moral shades of grey. The whole conceit of the nerve gas that can pick its victims by their genetic make-up is very similar to the chilling Janus virus in Channel 4's recent Utopia. The murky concept of 'the greater good' also comes up, despite things having descended by episode six into borderline armageddon. In an echo of his apparent treachery in The Claws of Axos, the Doctor at one point seems to side with Cassie and the Mega's plot, and indeed is seen as a traitor by the top brass at home. He has to appear to co-operate to an extent to save lives - including Jo's, and is every bit the clever, resourceful, and flamboyant Third Doctor we remember - bursting with moral outrage.

The whole tale is carried beautifully by Katy Manning and Richard Franklin, with Derek Carlyle and Bo Poraj in supporting roles, and directed by Ken Bentley. Manning in particular deserves props for not only her note-perfect performance as Jo Grant, but managing to evoke Jon Pertwee in the lines she reads for the Doctor. It's not perfect, but it's a testament to her considerable skill with voices. Franklin plays basically all of UNIT. His own performance as Yates is as good as ever, and his Brigadier in places evokes Nicholas Courtney very well. As for Benton, he doesn't have so much to do - but Franklin leans perhaps a bit too hard on John Levene's West Country accent and makes him sound like he's auditioning for The Wurzels.

Nonetheless, this is an excellent story, and well worth three hours of your time.