By Mark Jefferies Shirley Ballas says she enjoyed the “one-in-a-million” experience of being Rat on The Masked singer. The Strictly Come Dancing judge’s disguise fooled all the judges on the ITV1 show, including Davina McCall. Ballroom dancer Shirley, 63, said: “I wanted to step out of my comfort zone and see if I could sing. I was very nervous but I’m always nervous, even when I’m on Strictly. I get butterflies. “The audience was fantastic, everyone behind the scenes was amazing so the whole experience of being in disguise was, for me, one in a million.” Shirley said she may now carry on sing…