Detectives were called to Stowe School, whose former pupils include billionaire Virgin Group founder Richard Branson, after other members of staff raised the alarm about strange smells in the food last Friday."During routine checks, school staff became suspicious that foodstuffs had been tampered with and the police were alerted," said a spokesman for Stowe, set in 750 acres of impressive grounds near Buckingham. "We continue to cooperate closely with the police in their investigation." A Thames Valley Police spokeswoman said: "It was soup. It was being prepared for the pupils."  Detectives said a 58-year-old man had been arrested at his home on suspicion of administering poison with intent to endanger life or inflict grievous bodily harm.