The therapist.

The Therapist (portrayed by Lorelei King) was a Californian therapist working in London.

Kate suggested Lee visit her to get more in touch with his emotions. Lee found the experience uncomfortable as his use of humour had no effect on the therapist, who saw through his act with ease and that he had feelings for Kate. She suggested that Lee tell Kate how he felt and all he needed was the right moment. ("Death")