I rode half of it on Friday (Amberley to Eastbourne). It was wet and slippery in places and I had to push uphill in places that would be rideable in summer.
The grassy sections were a bit of a slog. It’s rained a fair bit since Friday so I think it would be slightly worse based on the rain over the weekend.
I’m a relatively strong rider and my moving time for 50 miles was 6 hours. I’d expect at least an hour off that in good conditions.
That being said, it was a really tough day out with all of the climbing. It’s made me rethink my desire to do the full thing in a day!