FIL dropped round today. When leaving my 3 year old said he wanted to go with Grandad. Grandad lives 3 mins away by car. He drives a nice car, Lexus Saloon. I asked Grandad if he had a booster seat in the back of his car because I had one sitting in the hall which he could take. He said no, sure I just always just put them on the arm rest that comes down between the back seat and then strap them in sitting on that". I was a bit I knew he would have put our 5 years old on it occasionally if stuck for a booster, but I was offering him one and there was no need for his to use that drop down armrest. I let it go cos they live so close and he would drive quite slowly but now I am annoyed with myself for not asserting myself and inisting on it. They all, (my dh included) think i am over cautious on this issue but (a) it is safer and (b) it is the law isnt it?? I didnt want to make an awkward situation by insisting but I think now that I should have insisted politely but firmly....why can't he just use the bloody booster anyway??