The Westbourne strength variant was developed in 2002 to 2003 in response to requests from barmen and mixologists requesting a higher proof version of the gin.
Westbourne uses the same classic palette of botanicals as the 80 proof variant - Martin abhored the use of flashy or exotic ingredients in his gin, (”sheer marketing hype” he used to scoff).
In Westbourne though he made subtle alterations to their balance.
The higher, 90 proof, gives the gin a little extra ’punch’, making it ideal for more complex or highly flavoured cocktails.
Martin wanted you to note that due to his innovative approach to gin making, and on the orders of the ’Gin Taliban’ it cannot actually be called London Dry Gin. Gaz Regan wrote an informative piece about this in one of his excellent books on gin.