see http://www.castlewales.com/narberth.html NB:Castlewales.com has oodles of relevant info on Narberth Castle,but it's photographs are no longer relevant as the whole site has been renovated ,repaired and made safe.As you can see from my pic,it is well maintained to a high standard.Well worth the visit; and it's free.
see http://en.wikipedia.org/wiki/Narberth_Castle
see http://www.onenarberth.co.uk/guidebook/narberth-castle/