CLICK). The final part of that trilogy airs this evening on BBC Two at 9pm. On BBC One at 8pm, another nature trilogy begins: Hidden Kingdoms (CLICK). This photo shows the size of an Elephant Shrew, called Sengi, compared to a Swallowtail butterfly. Purists might object to the use of blue screen backgrounds to create combined images as trick photography, but the result was cinematography of the highest order. Brilliant! And exciting.