Gareth Neame remembers casting actor as Lady Grantham and her ‘immeasurable’ contribution to show’s success

• Maggie Smith, Oscar-winning star of stage and screen, dies aged 89
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As I read the various drafts of Julian Fellowes’ pilot script for Downton Abbey, it was not lost on me that his new invention of the dowager countess (as yet uncast) bore some similarity to Lady Trentham in Robert Altman’s film Gosford Park.

That movie was a precursor to Downton in many different ways. My original pitch to Fellowes had been to expand on the premise of Gosford and reconceive it as a weekly episodic show. When it looked as though ITV were actually going to greenlight the series, our attention turned to casting.