Dad’s Army’s famous opening titles only came about following a row between BBC bosses, newly published archive memos have revealed.

The sitcom was originally to have started with shots of refugees and Nazi troops – but BBC One’s controller Paul Fox ordered them to be removed as he found them offensive.

They were replaced with this now famous animation of swastika-headed arrows advancing on Britain.

Michael Mills, the corporation's head of comedy in 1968, expressed his ‘profound disquiet’ and ‘shock’ at being forced to change the title sequence, which he thought was vital to show what the ‘valorous’ Home Guard could be up against.

He said it was ‘depressing’ that the comedy department was not allowed to explore new areas, in keeping with the progressive nature of the times, while other BBC output was becoming more adventurous.

‘I cannot help wondering whether we, in the comedy department, are controlled by different standards, i.e. clowns must stay clowns.’

The row is revealed in archive material released online by the BBC to mark the 40th anniversary of Dad’s Army.

As well as the internal BBC memos, the online archive also features a behind-the-scenes photo gallery and letters from the actors.

The documents reveal that the opening episode received ‘reaction index’ of 63 per cent, with viewers enjoying its nostalgia and authenticity, making it ‘excellent family viewing’, although a minority thought it was too farcical.

Jonathan Ross will be hosting BBC Two show celebrating 40 years of Dad’s Amry on Sunday at 7pm.

Visit the Dad’s Army archive here.