The 28-year old midfielder has finished a three-year stint in South London by heading up to Birmingham on a two-year contract and he is looking forward to the next chapter in his career with the promotion-chasing Blues.
"I'm absolutely delighted and buzzing at the moment. I can't wait to get going," he told the club's official website.
"It's been a hectic few days to get it done but this a positive move for myself at this point in my career and I can't wait.
"Hopefully we can improve as a team on last year (Championship play-off semi-finals) and go one better."