 Just before Cassandra leaves town , she tells Donna that Matt , the man who raised her , is not her biological father . Cassandra tells Donna that her real father is a man named Nick . In 2009 , it was announced that Donna 's father had been cast and would be introduced the following year . Brian Vriends was given the role of Nick Nixon . Of the introduction of Brian and Nick , executive producer , Susan Bower said " The Freedman family have provided fantastic drama for us so far and we have lots in store for Brian , it 's great to have him with us . This is just one of many , many great storylines we have coming up in 2010 " . Donna discovers that there are two men that could be her father and she contacts them both . Nick Nixon replies first and Donna begins to believe that he is her father . However , Professor Nicholas McKay ( Chris Bunworth ) later turns up and Donna becomes confused over the situation . Nicholas has just been released from jail and he is keen to do something right . However , he hurts Donna when he tells her that she is just like her mother and that she will run away . Robbie said " He takes a horrible approach " . Nicholas ' arrival makes Donna more afraid to find out the results of the DNA test she asked Nick to take . On the situation , Robbie said " She 's a hopeless romantic and wants the happily ever after – not only with Ringo , but with her family . " The DNA test eventually proves that Nick is her real father . 
