There may well be a case for a SURVIVAL SPECIAL (9pm ITV) on that most endangered of species, the Royal Family; this programme, however, restricts its attention to how Prince Charles runs his estate at Highgrove in Gloucestershire. Film-makers Carroll and Maurice Tibbles spent more than 18 months on these photogenic 1,112 acres, meticulously recording the changing seasons. Some of the film they ended up with, however, smacks of a promotional video for organic farming. Backed by soothing pastoral music, narrator Ian Holm comes out with such gems as, 'Manure is one thing there's plenty of on an organic farm like Highgrove.' The whole estate is organised along such sound lines; even the sewage treatment plant is an environmentally friendly mixture of bark chippings and reeds. PC Tudor Davies breaks off from his security duties to wire 82 bird-boxes to trees around the estate (nailing them in would be too damaging). But the producers needn't worry about bouts of blandness; they must know that the occasional ramble - actual and metaphorical - by the Prince, will prevent most viewers reaching for the off- switch.