Grand Slam is a general sports term applied when achieving something special.
Most common uses:
In tennis, winning the Grand Slam is winning the following four tournaments in the same year: Australian Open, French Open, Wimbledon, US Open. Those tournaments are therefore also known as the Grand Slam tournaments.
... served by the Metropolitan Line, District Line or Northern City Line (Great Northern & City Railway) remain open as mainline stations:
Great Missenden tub ...