Mash kumquats with cane sugar and the juice of half a lime in a thick glass (a caipirinha glass is best here) using a pestle and then fill up 2/3 with crushed ice.
Now pour on the gin, stir the whole thing with a long spoon and fill the glass up to the brim with ice.
As a garnish, some cane sugar can be sprinkled on the ice or decorated with half a kumquat, put one or two straws in and you`re done!
A little hint:
If you want the Bombay Crushed a little milder, you can defuse it with a little ginger ale!