He's quite a sturdy chap in his 70s. Mobility reasonable but needs a good chair to rest comfortably.
It needs to be comfortable, strong, light as possible and easy to carry and transport (he's going to use it at sporting events too so will move around).
I have an outwell chair, which was about £40 when I bought it, it is comfortable but quite bulky to carry about. It is a sturdy chair and so easy to get in and out of.
Any recommendations?