The first through trains to Porthmadog from Caernarfon run for Gold, Silver and Bronze sponsors on 30th October 2010. In January, February and March, you can sample trains from Porthmadog on the new section of the WHR. In Febraury half term, there is a full line service from both ends (Caernarfon and Porthmadog). See
bq.:http://www.welshhighlandrailway.net/index.asp
for full details.