Looks attractive, but checking at how the 1200km distance is 'split up' - returning to the nice hotel [Edit: hostel] being used Start/Arrivee/central 'sleeping' control - I was going to say "nightly" but probably better to say 'once a day'.
The first 'A' in FAQs says "It will run over three days beginning on Mid-Summers Day – Saturday, June 23rd 2018 at 06.00 hrs and finishing 90 hours later on the following Tuesday, June 27th." The route suggests day splits of 371km, 365km, 349km and 124km.
Since the start is at 0600 Saturday, the date/time to complete by is midnight on Tuesday 27 June (required minimum speed = 13.33kph).
For the full value rider (and the climbing will mean this applies to a fair proportion of the field) this implies (assuming (say) 16kph daytime average riding and, say, 4 hours sleep stop), sleeping 0510-0910 on the Sunday morning, sleeping 0800-1200 on the Monday morning, and sleeping 1000-1400 on the Tuesday, with 124km to finish off by midnight (at 16kph, with 100 minutes in hand).