Oil pressure warning light

It's a long time since I contributed to this forum. I sold my Disco to a relative. He now has a problem;

When braking the engine oil warning light comes on! At other times it's OK. The oil level is OK and up to the top mark. It has recently had a service and a cam belt.

Does anyone have any thoughts on this?

It sounds like the levels might not be right, or you may have a dodgy pressure switch (or wire). I would replace the switch as it's a cheap start and if it still continues just check the amount of oil in the sump.

I had a similar issue on an old Astra that I used to have. 280K miles and it used to use a bit of oil. I used to know I was running low because if I went around a corner a bit fast or braked hard the oil light would come on.

Thanks for that! I'll get him to check.