ZETA'S LAD can give multi-millionaire businessman turned trainer John Upson and his young jockey, Robbie Supple, the biggest moment of their careers by taking the English Grand National which is telecast live as the final event at Happy Valley tonight. The National - four-and-a-half miles and 30 fences of blood-curdling thrills and spills - may seem a bad race in which to have a bet. But in recent years the better-credentialled form horses have dominated proceedings and Britain's most successful professional punter, the late Alex Bird, always maintained it was the best betting race of the season. Unless the ground turns soft, it does look once again as if this will be a day when form horses come to the fore. But be warned. If you do want to back an outsider there is unlikely to be much value on the Hongkong tote. The bracketing of runners will trim the odds of the outsiders and it is best to bet these back in the UK.