Richard Madeley and Judy Finnigan are Taureans, born a few days away from each other in different years - Richard May 13 1956, Judy May 16 1948 - and their dark-horse move to Channel 4 is their birthday surprise. Taureans are noted for sticking things out and they don't usually relinquish their hold when they are on to a good thing. This Morning, a programme born under the marriage sign of Libra (launched October 3 1988), has been a perfect format for the everyday magic between them as a couple, and like all patient Taurean Bulls they would probably have plodded on into eternity if matador Maureen Duffy, ITV's controller of daytime programmes, hadn't waved one red rag too many.

Likeness is the mother of affection, so the old adage goes, and Richard and Judy are like hand in glove, with much in common. Not only are they both Taurus, but both have Venus, the planet of love, in the cosy, domestic sign of the Cancerian Crab. Good news, then, for daytime viewers, at home in their shells, scuttling along with plenty of personal, Cancerian emotion to make them feel secure. Nothing could be more conventional, some would say yawnsome, than this clingy, safe-bets Taurus-Cancer combination, so what has given the show its poke for the last thirteen years?

Richard's chart shows that he likes to see himself as the clever Dick of the duo, and his Mercury connections with This Morning indicate an endless supply of observations and curiosities. Left to his own devices, he is liable to chat on in the same mould, uninterrupted, until at least 2017. Yet the astrology suggests that Judy has been the key to This Morning's success, with Richard as a necessary bit part in her movie. The programme's appeal comes from Venus, placed on Regulus, the Royal Star at the heart of the lion in the Leo constellation. This makes the programme a winner by mysteriously triggering an archetypal response in its viewers, the 'IT' thing that no-one can ever quite explain. Judy's Mars is on the same Royal Star and therefore exactly on the show's Venus, making her its magnetic attraction. This Leo Mars can also be proud and wilful, with an aggression that is not always obvious and a prima donna haughtiness difficult to accommodate.

Add this to the stubborn streak inherent in Taurus and Richard and Judy can lock in to an entrenched, possessive position. After thirteen years tenure at Granada, it would have been impossible for them not to see This Morning as their child, and theirs only. When Taureans find it difficult to let go, they repress change and defend against it until disruptive events come at them from the outside:

" there is usually a bee in the flowers...Often the Taurus himself courts this bee without realising it, unconsciously setting up a situation where he is shocked aware while thinking it happened by chance or was someone else's fault." (Liz Greene, Star Signs For Lovers).

Unluckily for Maureen Duffy, she has been projected into this role, the bee in their flower. Since last summer, Uranus the outsider planet of independence and defiance, has been triggering adventurous Jupiter, moving Judy's psyche away from a predictable, middle-of-the-road image. We can see the first hint of trouble in her little mishap at the National Television awards last autumn: at the very moment of receiving accolades for This Morning, something pops up to warn us that all is not as securely contained as we might imagine. If her bosses at Granada had been reading the omens, they would have known then that Judy was threatening to let it all hang out.

Most commentators reckon that the move to the Channel 4 genre won't work, but there are no immediate wobbles in the astrology so Judy can allay her fears that she has made a wrong move. Yet there is no room for complacency or churning out old formats. Both horoscopes are dominated by radical Uranus for several years to come, so tune in to see a new-look Richard and Judy, with attitude.