Wimbledon - highlights : Murray/Williams - Mies/Guarachi
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The duo - dubbed MurRena or SerAndy by fans - have won their first two matches, seeing off Alexa Guarachi and Andreas Mies in the first round and Fabrice Martin and Raquel Atawo in the second.
Williams is also in the semi-finals of the women's singles draw and Murray has been inspired by the professional and competitive approach she has taken.
"You expect someone who has been as successful as she has to be extremely competitive - and she is," he wrote in his BBC Sport column.
"Even though it is mixed doubles, and her priority is singles, she goes out there and wants to win every point.
"Her record speaks for itself and the more matches she plays, her performances and level will only increase.
"What I think has worked particularly well so far is our returning games. Some of Serena's returning - especially in our second match - was brilliant.
"I didn't know her particularly well before we played and we have not spent loads of time together.
"Playing alongside Serena at Wimbledon has been great fun so far."
Brands Hatch, 2017