ICT 2 Visa Extension within UK - Expiring Passport

Hi,

I am currently working in UK on a ICT 2- Long term Visa and my current visa is getting expired on 14/03/2016. My current employer has agreed to provide further 18 month extension on the same category.

Issue:
My current passport's validity is till 26/03/2017 only. If I apply to extend my UK visa under ICT 2 Long term category for next 18 months (which should be till sep/2017), will UKBA grant visa extension for further 18 months completely (even if my passport gets expired on 26/03/2017, which I am planning to renew in 2017 in UK itself) (or) will UKBA grant visa extension only for next 12 months (till Mar/2017) taking my current passport expiry date into consideration (which is on 26/03/2017) ?

Could you please ASAP suggest me the best approach to get full 18 months extension.

The expiry date of the passport has no bearing on the duration of visa. You will get a 18 month visa.