Ok, I've been looking at the iplayer app and have picked up the Centre Court from there, no mention on my app that this is 4k, although when I selected it the initial went black quickly and a sharper version appeared. Looks pretty good but no specific ref to it being 4k.
I've set the iPlayer back to "normal", not Beta. Re-booted V6. Still no mention of UHD on the Centre Court option on iplayer, either on the screen where the courts are listed or on screen from the Centre Court feed.
If you are watching the 4k hdr stream,it says bbc uhd in the top right hand corner
When I was watching the England v USA World Cup game last night in 4K on iPlayer, nothing showed on the screen to signify the stream was in 4K other than my own TV's 'Info' banner (or does this only happen for HDR content)?!