Is someone with HIV, cancer or multiple sclerosis protected from disability discrimination only at the point that the condition affects their ability to carry out day-to-day activities?

No. Under para.6 of sch.1 to the Equality Act 2010, people diagnosed with HIV infection, multiple sclerosis or cancer are deemed to be disabled whether or not the condition has yet begun to have any effect on their ability to carry out day-to-day activities. The rationale behind this is that these conditions can stigmatise sufferers from the point of diagnosis, as well as having a huge personal effect on them.