So naturally this was followed by a close-up kiss.
The kiss was well received by UK fans.
However, BBC Entertainment, which broadcasts Doctor Who in Singapore, Hong Kong, Thailand, and South Korea, cut the kiss from the broadcast.
BBC Worldwide owns the BBC Entertainment channel.
So what specific regulation does the kiss break? The Singapore MDA lists the following rules for its free-to-air broadcasts.
If BBC Entertainment has a subscription licence, it would have to follow this regulation.
Update — 1 September 7.45pm BST: BBC Worldwide had to comply with subscription licence MDA regulations, so that Doctor Who did not breach the code.
The rules state that "homosexual themes" can be allowed for audiences over 18 years of age (listed in their regulations as M18). As Doctor Who is a family show and is not directly aimed at an adult audience, the scene could not be shown.