Runaway US Open winner Rory McIlroy has booked his place in October’s Grand Slam at Port Royal but he will have to decide whether to accept the invitation.The Northern Irishman became the youngest Open winner in 88 years when he carded a record 16-under par finish on Sunday at the Congressional Country Club in Bethesda, Maryland.He joins South African Charl Schwartzel who won the Masters, where McIlroy led heading into the final round before a dramatic collapse.The Slam is designed to feature the four winners of golf’s majors over two rounds.Still to come are the British Open next month followed by the PGA Championship in August.In recent years, several major winners have opted out of the Slam, including Tiger Woods.Last year’s winner was alternate Ernie Els.See US Open report Page 25.