The adult actors learned their scripts as normal, but the child actors were given only last-minute instructions by the writers instead of full scripts, in order to achieve more natural, semi-improvised performances.

Outnumbered marked the first collaboration between writers Andy Hamilton and Guy Jenkin since their previous show Drop the Dead Donkey ended in 1998.

Co-creator Andy Hamilton said he saw about 30 children before narrowing it down to the perfect three young leads.

Ramona Marquez, who plays Karen, was cast after she was spotted in the same class as Guy Jenkin's twin sons; Jenkin's wife suggested he meet her because 'she's got something'.

The series is set in Chiswick, West London, but was actually shot on location in Wandsworth, with the exterior of the family house filmed on Dempster Road.

After the fourth series aired, actor Tyger Drew-Honey suggested there might not be a fifth series because he and the other child actors were outgrowing their roles, prompting the BBC to publicly confirm that talks for a new series were already underway.

Reviews were initially mixed, but grew more positive after the second series; The Daily Mirror compared its low-key, mundane style to Seinfeld and its improvisational scenes to Curb Your Enthusiasm.

The pilot episode drew 4.1 million viewers (25.5% audience share), well above the average 2.2 million typically attracted by shows in its time slot.