Nathan Flear posted the route:
The Welsh Three Peaks Challenge takes in the three peaks of Wales: Snowdon (Yr Wyddfa) in the North, Cadair Idris in mid-Wales, and Pen y Fan in the South.
It includes a total running distance of 17 miles (27.4km) with an ascent of around 1500 metres (4920ft), there is also around 4.5 hours of driving in between. If you bicycle between the peaks, it is about 89 miles between Pen y Fan and Cadair Idris, and another 45 miles between Cadair Idris and Snowdon. In either case, your time starts at the TH for the first peak, and ends back at the TH when you have completed the final peak.
I'm not sure if anyone out there knows of an existing FKT on this, I have spoken to Three Peaks Challenge UK who register records and they have said they don't know of any particularly notable times.
The "Double" is specifically for cycling between the THs. Starting from the first TH, hike the first peak up and down, cycle to the second TH (Cadair), hike that one up & down, cycle to the third TH, hike that up and down TWICE, cycle back to the TH for Cadair, hike that up & down, then cycle to the last peak and hike it up & down before stopping your watch! In total this is 268 miles of riding with 15,426ft of elevation, plus 33.4 miles of running with 15,314ft of elevation, totalling 301.4 miles and 30,740ft of elevation. (Proposed by Brad Willis)