A coupling assembly for enabling transfer of an article (18) from a first support structure (11) which carries the article (18) in a first operating mode, to a second support structure (40) which carries the article (18) in a second operating mode in the absence of the first support structure (11). The coupling assembly includes a first coupling member (23) which is releasably connectable to the first support structure (11), the first coupling member (23) being securable to or forming part of the article (18); and a second coupling member (30) securable to the second support structure (40), the second coupling member being adapted to adopt a first, receiving position to receive or release the first coupling member (23)and a second, holding position to secure the first coupling member (23), such that when the first coupling member (23) is held by the second coupling member (30), the first support structure (11) can be released from the first coupling member (23) so that the first coupling member (23) is carried by the second coupling member (30).