Downton Abbey: Meet the new cast
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The 28 year-old British actress willl join Downton as a live-in nanny for the child that Sybil died giving birth to.
Daisy, who will reportedly join as a lead character, has already starred alongside Maggie Smith and Hugh Bonneville in From Time To Time, a 2009 feature film also written by Julian Fellowes.
She has also appeared in Doctor Who and Lewis as well as 2011 film Pusher alongside Agyness Deyn.