Start the hike from the car park opposite Storey Arms Centre (on the A470, 15-20 minutes from Brecon).
(S) Cross the road, pass the gate and make your way uphill due north-west keeping the forest on your right-hand side.
After thirty odd minutes you'll start to see the Corn Du (873 m), the first peak of the day. However, you'll need to head downhill over 5 m and cross a ford in order to reach it.
(1) From the stream, the slope is steeper but is not difficult (wide track).
(2) Approximately 30 minutes later, you'll come across a large ridge overlooking a vast cirque and the outskirts of Brecon laying at the back of the fields. You can spot a beautiful lake further down to your left, Llyn Cwm Llwch, and to your right, behind Corn Du, Pen y Fan. You'll also notice sheep climbing on impressively steep slopes that would make even ibexes jealous!
The path continues to the right heading south-east up the ridge reaching Corn Du.
(3) At the top of Corn Du, keep going along the ridge due north-east. The trail goes down a few metres reaching a pass then heads up again reaching Pen y Fan.
(4) The view must be breath-taking from Pen y Fan... unfortunately, we were surrounded by fog so didn't get that chance to see it...
(5) You'll get to another pass by an intersection. Follow the main path which heads down the mountain side due south-west. It's a quick descent which leads you to the initial forest to the left.
(6) After crossing a bridge over the stream, you'll get to a car park on the edge of the A470. Head up the track which goes along the forest (north-west) reaching your starting point within a few minutes.