Has this been mentioned since the other series, I got then feeling he was going to be a recurring character but nothing seems to have come if it since the bells of St. John episode

Did you miss The Name of the Doctor?

And The Snowmen.

The snowmen was before but yes you're right I had completely forgot about in the name of the Doctor.

GI was a very old villian, from Patrick Troughton's era. I (or my DS user name) was the first to discover him, in a Tibetan monastery.

i wish the GI would come back with the yeti