In the UK you may sack someone, for any reason, during the first 12 months (well actually it's 11). Any manager who hasn't discovered that he has employed a donkey in this time deserves to have the right to fire someone taken away from him. FWIW in Germany you put someone on an initial three month's probation at the end of which you must either confirm their permanent status or dispense with their services (an extencion to the probation period is not an allowed option) AIH many UK companies work a probation period, but it has no status in law.
Tim