David Walliams talks about returning to school for a second series...

Are you pleased to be back in Mr Church's lab coat at Greybridge once again?

It is great to be doing the series again, particularly getting everyone back together as it is such a brilliant cast. It is great to be back and it is wonderful to see the actors bring the characters to life so brilliantly once again.

Where do we pick up the story following the school trip to France at the end of the first series?

We pick up the story at the start of the new term after Mr Church and Miss Postern have a disastrous date over the summer holidays. Mr Church and Miss Postern had made an arrangement to go for a meal but unfortunately turned up in two different branches of Bella Italia so they get off to a frosty start! Therefore at the beginning of the series Mr Church has a lot of ground to make up to try to get back into Miss Postern's good books. Meanwhile, Miss Postern herself is trying to work out what she wants to do with her life, either carry on being a teacher or have a baby.

Mr Church is at heart a conscientious character and does take his responsibility as Deputy Head of Science very seriously. Do you think he needs to perhaps loosen up a little in order to woo Miss Postern?

Mr Church is very uptight! I think that is why he has probably never had any success with the opposite sex his entire life. He is very set in his ways and he is someone who has never had a partner before. If you've never shared a house with anybody and if you have never been married I think there is a danger that you will get set in your ways. Mr Church would probably find it really difficult to adapt to being with someone.

I also don't think you actually really want them to get together as it would spoil the tension between them.

Tell us about what is happening with Mr Barber - he wasn't in a very happy place throughout the last series! Do things continue to get worse this time round or is there light at the end of the tunnel for him?

Mr Barber was the geography teacher that was down on his luck and struggling throughout the last series. Over the summer holidays he has had something of a nervous episode and has been demoted to caretaker. But like Peggy in Hi-De-Hi! who always wanted to be a yellow coat, he wants to get back to being a geography teacher. So we follow his story over the series of his struggle to get his life back on track.

There are some great guest stars appearing this series, can you tell us a little about them?

Jack Carroll, the brilliant comedian who came second on Britain's Got Talent last year was perfect to play a kid in this series and he was really funny. Myself and the Dawson Brothers wrote the part with him in mind and we had a lot of fun writing material for him. Jack will appear a little later in the series and I don't want to give too much away as he plays quite a surprising part! I've stayed in touch with Jack and his mum ever since Britain's Got Talent and I am delighted that he wanted to be part of the series.

Also, a childhood hero of mine, Michele Dotrice, who played Betty in Some Mothers Do 'Ave 'Em, plays Mr Gunn's mum and she was absolutely brilliant. Everyone on set was so excited we had someone so legendary with us.

We were also very lucky to have Morgana Robinson playing the part of a visitor who comes to Greybridge to give some careers advice to the pupils in the first episode. Morgana is a fantastic comedian who had her own series on Channel 4 and she has a big scene with Catherine - it was brilliant to see them together.

Is it important to you to film in a real school?

It is really important to film in a real school because when we were thinking about the series first time round we had a big question as to whether we would film in a studio in front of an audience or whether we would do it on location. I personally felt that we wouldn't be able to convincingly portray a school in a studio, plus the audience are so familiar with the classroom situation that it would immediately look unrealistic, so we decided to film at a real life school.

Brilliantly, the real life school that we filmed in was able to provide us with around 200 child actors which is usually pretty hard to come by. It gave a real reality to the series and I think it really helps the cast too as addressing all of the children during the big assembly scenes in a real school hall makes you feel more like an actual teacher.

A lot of the characters you have played in the past involve lots of extravagant costumes and sometimes prosthetics, meaning long periods in hair and make-up before getting on set. Is it refreshing to play one character for an entire series?

Little Britain was such a big hit and it is always tricky to know how to follow something like that so the most sensible thing to do was something completely different. I wanted this series to reveal a bit more of myself as an actor with perhaps not so many layers of glasses and prosthetics, so for Big School I didn't want to be hidden under all that.

I also wanted to write a more grown up story, a love story in fact, and to be a little more empathetic with characters that people will hopefully really care about that and the audience will want to see do well.

Have you got a favourite character that you enjoyed writing for or playing opposite?

I love writing for Miss Postern. Catherine's performance is so perfect and so funny that I have to stop myself from laughing when she is doing it. The joy of writing for someone like that is knowing that she is going to do something amazing. A good example was writing a scene that required her to speak Chinese. I knew when it was being written that she was going to be brilliant at it. It is a joy writing for her especially.

I also love writing for Ms Baron as there is such a brilliant music to Frances de la Tour's voice. In fact, it is simply incredible just working with someone like Frances as I can't believe I have even met her let alone being able to work with her.