The House of Lords has published an important decision on disability discrimination law, Lewisham v Malcolm [2008] UKHL 43, that turns much previous authority on its head. The particular case concerned housing: Malcolm was a secure tenant of the local authority, but he left his flat and subletted it. This had the legal effect of cancelling his security of tenure and converting his tenancy to a contractual one. The local authority served notice and brought a possession claim. Under normal circumstances, since the subletting was a breach of the tenancy, the local authority would be successful.

Malcolm's defence was that he had breached his tenancy agreement as a result of his schizophrenia, and that he was disabled within the meaning of the Disability Discrimination Act 1995. Section 22(3)(c) of the 1995 Act provides that evicting a person from housing is unlawful if in doing so the landlord discriminates. Section 24 the provides that discrimination will exist if "(a) for a reason which relates to the disabled person's disability, [the landlord] treats him less favourably than he treats or would treat others to whom that reason does not or would not apply; and (b) [the landlord] cannot show that the treatment is justified."

This statutory wording has been the subject of much dispute over the years - if Malcolm's case is right then the council cannot evict him for unlawfully subletting his flat. Nor could they (or any other landlord) evict a tenant for falling into arrears if this was due to a disability.

The House of Lords addressed the following issues:

• Does the reason for the eviction "relate" to the tenant's disability?

To determine this question the Lords followed the usual practice of looking for the non-disabled comparator. In this case, the correct comparator was a person without a disability who had nonetheless sublet the flat and moved out. Since the local authority would have treated this person in exactly the same way, it could not be said to be treating Malcolm "less favourably" such as to give rise to a claim of disability discrimination.

• Is it relevant whether the landlord knew of the tenant's disability?

The Lords' view was robust- the local authority must have knowledge (or imputed knowledge) of the disability before it can be said to have discriminated. This ruling resolves a considerable a number of conflicting authorities.

This is an important judgment, as it relates not only to housing, but to employment law, education, transport and goods and services.

Written by Joseph Neville, Barrister at New Walk Chambers specialising in Employment Law.