Dropped off with Elin and Huw at Porth Penrhyn. Great surface gently uphill to start. Some good practice singletrack down nearer the Afon Cegyn. Roots, stumps, etc on muddy singletrack with some neat little bridges made of concrete sleepers. Kids loved it.
Route up to Bethesda is good, even the on-road section.
Must go back and finish to route from Penrhyn Quarries up to Ogwen.