Alexander Armstrong, the voice of super-computer Mr Smith in The Sarah Jane Adventures, has promised fans that they won’t be disappointed by the forthcoming series.

The actor told DigitalSpy that he’s currently recording his lines for its 12-part fourth series, which is set to begin airing on CBBC this Autumn. He teased: “This very afternoon I’m heading back into town to voice more. There’s some brilliant things coming up. I’ve done the first four episodes, which were great.”

He also offered some hints as to just what we can expect to see in the new adventures, the titles of which were unveiled by Doctor Who Magazine back in June. He said: “Luke goes off to Oxford University and there’s some intrigue surrounding that. There’s a nasty nightmare creature. And K-9 goes off with Luke – there’s a very sweet moment between Mr Smith and K-9. They sort of admit their grudging respect for each other.”

He also admitted that he’d give his “eye-teeth” to appear on-screen in the spin off.