Chepstow to Holyhead 193 miles
In September 2020 I cycled the Welsh End to End.
I started at Chepstow, on the border with England, and cycled through the beautiful hills of the Brecons, mid-Wales and Snowdonia (mostly along the Lôn Las Cymru) up to Holyhead, where the ferries depart for Ireland.
So it was an End to End in many ways. Border to border; bottom right to top left; southeast to northwest; bridge to ferry.
The total End to End distance was 350km (220 miles) with 5000m (16000 ft) of climb over six leisurely days.
Cardiff to Holyhead 237 miles
In a very wet June 2000 I cycled the other variation of the Wales End to End via the Lôn Las Cymru, starting from Cardiff.