And the 25-year-old, who was also shortlisted for the IRB Player of the Year award, joined the illustrious company of fellow Lions Martin Johnson, Jonny Wilkinson and Sam Warburton by claiming the gong.
"Leigh was a convincing winner of our vote and a worthy recipient of the award not only for his performances for the Lions but his displays in the Six Nations earlier in the year," said RUWC chairman Adam Hathaway.
And the result came just a day after a ringing endorsement from Toulon fly-half Wilkinson.
"Leigh is a fabulous player and is a true professional," said Wilkinson. "I saw him before the Cardiff Blues game when I got to the ground and he was already there practising. I love to see that and it shows how precise he is and his attention to detail."