What could be in store? Pam Ferris and Jessica Raine get back to work filming the second series of period hit Call The Midwife

Last series it was a sure fire hit, even beating Downton Abbey in the ratings war during its season one finale.

And now anticipation is mounting as the stars of Call The Midwife were spotted started to film the second series this week.

Lead stars Jessica Raine and Pam Ferris have thrown themselves back into work in their 1950s-based characters.

They're back! Jessica Raine and Pam Ferris return to film hit show Call The Midwife as they begin to shoot the second series in London

They're back! Jessica Raine and Pam Ferris return to film hit show Call The Midwife as they begin to shoot the second series in London

Looking like something out of movie Sister Act, 64-year-old Ferris was seen in full nun get-up, including a cross around her neck.

She was seen cycling up the road as they took to the streets of the Southbank in London.

Pam was joined by co-star Raine, who plays nurse Jenny Lee on the popular series.

In character: Pam Ferris is seen in full nun costume cycling through the Southbank in her role as Sister Evangelina

In character: Pam Ferris is seen in full nun costume cycling through the Southbank in her role as Sister Evangelina

The younger star slipped back into her blue nurse costume with a red cardigan as she pushed a vintage-style pram up the street next to Ferris' character Sister Evangelina.

The BBC commissioned a second series of the programme after it grew its audience from 9.8million to 11.4million watching the sixth and final episode, which aired in February.

Set in a fictional nursing convent, the series follows Miss Raine’s character Jenny as she works as a newly-qualified midwife in a deprived part of East London in the 1950s.

Anticipation mounting: Jessica Raine, as nurse Jenny Lee, throws herself back into character following the first series being so successful it took over Downton Abbey during its season finale in February

Anticipation mounting: Jessica Raine, as nurse Jenny Lee, throws herself back into character following the first series being so successful it took over Downton Abbey during its season finale in February

Back in time: The streets of London are transformed once more to mimic the 1950s style of the show, which is due to hit screens again at the start of 2013

Back in time: The streets of London are transformed once more to mimic the 1950s style of the show, which is due to hit screens again at the start of 2013

It also stars comedienne Miranda Hart as hapless toff Chummy and Jenny Agutter as Sister Julienne. 

A second series of the drama – based on the memoirs of Jennifer Worth, who died last year having sold more than a million copies of her book – began filming in June.

Miss Raine has said: ‘The BBC want me to sign to do eight more episodes, but it’s not all done and dusted yet.

‘I might, but it’s very much up in the air at the moment.’

Not long now: Filming of the second series began in June after the BBC commissioned another series following its successful debut

Not long now: Filming of the second series began in June after the BBC commissioned another series following its successful debut

On a high: The last series ended with Miranda Hart's character Chummy Browne finally walking down the aisle after years of being unlucky in love

On a high: The last series ended with Miranda Hart's character Chummy Browne finally walking down the aisle after years of being unlucky in love

The last series ended on a happy note with Hart's character finally getting married following years of being unlucky in love.

Consolidated figures – which take into account viewing on personal video recorders – indicated that more than 10 million people watched each episode of series one.

This makes it the most-watched new BBC drama since its current measuring system began in 2001, the network said today.

Which makes it more popular than Sherlock Holmes, Doctor Who and the first series of Downton Abbey.

The next series is planned to air next January and February.