Jack Sellen (CIOL), Nov 18th 2014, 14:13 Verified Guru
I don't think it's about how many languages you know; they look at your complete range of "competencies". I understand that having a foreign language is not a requirement for some FCO roles, but you will be able to apply for a greater variety of roles if you have one or two foreign languages. The better you can demonstrate that you have the ability to learn languages the more likely you are to be picked up.
You might find this article interesting as it describes the on-the-job training available.
Jan Krauss, Nov 18th 2014, 17:49 Verified Guru
Speaking a foreign language you could also consider the European Fast Stream which I believe the FCO has re-instated (it was scrapped at one stage)
This is basically like the normal fast stream but you are earmarked for a role in the EU institutions. If you get in, the FCO will help prepare you for the EU recruitment competitions which are tough.