Modern Welsh is descended directly from Brythonic Celtic. The language and all its changes settled into more or less its current form by 14th Century (‘middle’ Welsh) mostly forming in the 8th century (‘old’ Welsh) and anything before it is (‘Ancient’ Welsh) or simply ‘Brythonic’.
a, b, c, ch, d, dd, e, f, ff, g, ng, h, i, l, ll, m, n, o, p, ph, r, rh, s, t, th, u, w, y
The Welsh alphabet has 28 written letters (missing the English J, K, Q, V, X and Z but supplementing with ch, dd, ff, ng, ll, ph, rh and th). Reading Welsh becomes a whole lot less intimidating when you realise that W and Y are used as extra vowels (‘oo’ and ‘uh/ee’ respectively) and speaking it becomes easier if you learn a few simple consonant sounds.
Terrifyingly, the decision to drop K from the Welsh alphabet appears to have been a practical business decision made in the 16th century when the printers of the New Testament in Welsh didn’t have enough ‘K’s to meet the text’s needs. They were replaced with Cs in a very unpopular move and the habit stuck. Just goes to show how easy it is to bastardise language.