A common trope in The Sarah Jane Adventures, and indeed Doctor Who for that matter, is that the second installment of a two-parter rarely lives up to the promise of the first episode. Sadly, The Eternity Trap does not buck this trend.

It's a not a massive drop from the opening gambit but it's significant enough to comment upon. This part actually feels like a lazy sequel with scenes played out again and scares repeated accompanied by slightly tired Ghostbusters references and the odd laugh (courtesy of gag-smith Clyde).

Part two also suffers from some poor performances, notably Donald Sumpter, whose Erasmus Darkening excited greatly yesterday but once this guy gets his blah-blah-blah on he comes off as a pantomime version of the Emperor from Star Wars. Also disappointing is Calum "Yup, Zod from Smallville" Blue who gives new meaning to the word 'bland' in his portrayal of the 'heroic' father, Lord Marchwood.

Thankfully, Clyde (who amusingly describes the happenings as a "super spook smackdown") and Rani, played by Daniel Anthony and Anjili Mohindra respectively, are on top form, making an entertaing couple as they gag their way through the scares with one-liners like "How do you distract a ghost? Find him a pretty ghoul-friend."

The denouement comes and goes without much incident and you'll remember the atmosphere and ambience set up in the first part long after you've forgotten the characters and plot. A great pity as The Eternity Trap looked like it was going to rank amongst the very finest offerings from The Sarah Jane Adventures.

Read our review of the last episode here.