"Though I am allowed to be excused from this if i can prove that i am living here in Enlgland legaly. "
Interesting stuff really!
In other words, the government (of your origin country) has a right to call you back to that country to work for them, if you are here in UK illegaly
Frankly, that is very nice of your country of your origin. Which country is it?
If all other countries had this sort of right to call back their citizens who are illegals in the UK, the problem of illegal immigration would be solved immediately (or would it???
)
Anyway, my answer to your question will be:
1. Your passport and an appropriate visa - i.e. these days, a "residence permit" sticker in your passport.
2. If you are from another EU country, then your Identity card from that country (if your EU country has ID card system in place) will also do, since if the card describes you as a citizen of that EU country, it is enough to prove that you have the right to live and work in the UK.
3. Or even an UK HO issued work authorisation document ( i have heard about such a document, but don't really know what it is about).
I can't think of any other documents that you can use to prove you are legal in the UK.
Wait for other members comments.