Andy Galbraith works at the National Antiquities Museum as an appraiser.
Alex works alongside Soo Lin Yao at the Museum and has a crush on her even asking her out before her disappearance, which she says no to. Some time after that he is approached by his boss and is asked to appraise two Chengua Ming vases up for auction at Crispian's, He suggests that Soo Lin Yao would be a better choice as she is the expert but learns that she suddenly resigned her job out of the Blue.
Worried about what could have made her quit so suddenly, he visits her flat and leaves a note for her which Sherlock and John later find and interview him about. He does not believe that she would quit as she was in the middle of an important piece of restoration and doesn't accept the "family problems excuse" as he knows she doesn't have any family.
When talking to Sherlock and John, He explained the tea ceremony to them, helping Sherlock to realise that Soo Lin was hiding in the museum.