In general, unflavored gin, not from a wine source, does not require a Hechsher. Please note why the KF removed its Hechsher from Tanqueray Gin in the following email…
FEDERATION OF SYNAGOGUES
65 Watford Way, London NW4 3AQ Tel: (+44) 020 8202 2263 Fax: (+44) 020 8203 0610
E-mail: firstname.lastname@example.org Website: www.kfkosher.org
EMAIL: email@example.com REF: MDE/LL/KB 16.0294
22nd January 2016
Rabbi Eliezer Eidlitz
Dear Rabbi Eidlitz
Thank you for your email.
The unflavoured Tanqueray Gin is produced by making use of vats which are sometimes also used for wine based products. There is a problem of Kovush, but obviously it is Aino Ben Yomo.
Consequently, I would not say that the product is treif, but obviously we will not give a Hechsher to it.
Dayan M D Elzas
Director of Kashrus