Does this count as sub-letting? Legal defintion anyone?

[Helen Mac]

I wonder if someone could help me. I am a tennant and have lived in the flat for 2.5 years and have always been responsible for finding new housemates once the previous one has moved out.
My landlady considers me to be the main/only tennant and that i am 'sub-letting' the rooms to other housemates. She is happy with this arrangement as she trusts me and it's easier for her than looking for new housemates. Despite this, other housemates pay rent directly to the landlady and not through me.
I have asked one of the housemates to leave for personal reasons. They are refusing. Do I have any rights to 'evict' them seeing as the landlady views me as the main tennant and them as a sub-tennant? The landlady does not want to get involved in what they see as a dispute between myself and the housemate
I have a contract. The new housemate does not, but is pushing for one to protect themself.
What is the legal situation please? Thanks.

[Beeber]

The Shelter website has info about sub-tenants which indicates that this area is complex.

More experienced posters may be able to confirm whether the fact that the head landlord (owner) accepts rent from the sub-tenant makes their tenancy fully legal and the relationship directly with them, rather than you. I don't know.

http://england.shelter.org.uk/advice/advice-2939.cfm

Your flat mate will have certain rights and protection enshrined in law even without a written contract which covers eviction/repossession.

[Planner]

I would speak directly to the Landlord so that you can both present a united front to give this person any required notice etc. I assume due to the length of your tennancy and your obviously good relationship with the LL this shouldnt be a problem? Would it be also worth disscussing payment arrangements with the LL to avoid this kind of situation in the future? i.e you get all the rent and pay it in one lump sum?