Let me just clear something up...it's a common mistake

A learning disability - mental handicap, or mentally retarded as it used to be called in a murky depths of a not very nice linguistic past - is very different from mental illness.

Tom is not mentally ill. He has a learning disability, which, for my parents was hard work. For me, it meant growing up with a brother who was more complicated and challenging than most, who could not always communicate his needs and desires and who required extra care, compassion and understanding: he was terrible at playing shops but very good at kicking fights and eating crisps. So we always found a way to play together. The extra care and understanding required of me as a sister wasn't always there when I was a kid, and sometimes still he doesn't get from me now. If you can look beyond the disability he's just another regular guy who has a beautiful lack of the mannered artifice and bullshit, which seems to coat a lot of ordinary life. He still has enormous value as a human being, but getting to that value takes more effort than just small talk and checking out where his jeans are from (usually Tescos, if you're interested).

I'm seeing Tom this weekend and I'll get some words from him. But meanwhile this is how the UK's biggest LD charity Mencap defines it, significantly better than me:

A learning disability is caused by the way the brain develops.

There are many different types and most develop before a baby is born, during birth or because of a serious illness in early childhood. A learning disability is lifelong and usually has a significant impact on a person's life.

Learning disability is not mental illness or dyslexia.

People with a learning disability find it harder than others to learn, understand and communicate. People with profound and multiple learning disabilities (PMLD) need full-time help with every aspect of their lives - including eating, drinking, washing, dressing and toileting.

There are 1.5 million people with a learning disability in the UK. Like all of us, they are individuals who want different things in life and need different levels of support.