Nigerian market trader allegedly trafficked to London has told a jury he was shocked when a doctor revealed he was there to donate a kidney.   The man, who cannot be named for legal reasons, said he thought he was coming to the UK for work.   At the Old Bailey, Nigerian politician Ike Ekweremadu, 60, has denied breaking modern slavery laws.   He is accused of bringing the 21-year-old to the UK to provide a kidney for his daughter Sonia.   His wife Beatrice, 56, daughter Sonia, 25, and associate Dr Obinna Obeta, 50, also deny conspiring to arrange…