Few stories tear at the heartstrings quite as much as the tragic tale of Tommy Jones. In August 1900 the five-year-old and his father were walking from the railway station in Brecon to his grandfather's farm in Cwm Llwch. They rested a while at the army camp at Login where Tommy's grandfather and his 13-year-old cousin, Willie, met them. The two men decided to stay a while with the soldiers but the two boys continued on to the farmhouse, 0.5 miles (800m) away. As darkness fell, Tommy got scared. Willie wanted to continue to the farmhouse, but Tommy decided to return to his father. Sadly, he never made it. Willie rejoined the men shortly and, realising that the boy had vanished, a huge search ensued. The scale of the search increased as the days went by. There were even suggestions that he'd been kidnapped or murdered. Remarkably, a few weeks later, a local woman dreamed about the boy and, although she had never been there before, was able to lead her husband up on to the ridge where they discovered Tommy's remains. A simple stone obelisk was erected close to the spot where the body was found. It was moved slightly in 1997, as the area surrounding it had become badly eroded.

Spectacular route

This is far and away the most spectacular route up on to the highest ground of the National Park. The jagged ridges, steep gullies and deeply gouged valleys pay more than a passing resemblance to those of the higher mountains of Snowdonia, many miles further north. It's only the popularity of the peaks, which are easily reached from the road, which prevents it from feeling like a really wild day out in the mountains. The biggest climb comes early on, with a steep pull up from the car park on to the head of the lovely and remote Cwm Gwdi. The path then follows rocky, disused quarry tracks before hurdling the grassy spur that leads on to Cefn Cwm Llwch. The ridge is by no means knife-edge, but it does feel incredibly airy, dividing two magnificent valleys, both cradling fast-flowing mountain streams. The rocky ramparts of the summit seem to taunt you as you continue southwards and then, as you reach the steep final step, the spectacular north east face of Pen y Fan presents itself in its full glory. This is probably the most magnificent section of mountain scenery in the whole National Park. Steep gullies drop down from the summit, vaulting vertical crags as they plummet into the valley below, and ravens play on the ever-present updraughts. The summit, often crowded, can come as an anti-climax after the wild scenery you've just witnessed, but it's a great mountain and there's plenty more on the descent from Corn Du. After crossing the void between the peaks, you'll trace the airy tops of Craig Cwm Llwch past the Tommy Jones obelisk, one of the Beacons' best-known landmarks. You'll then drop to a fine example of a glacial lake, Llyn Cwm Llwch, which makes an excellent picnic spot, surrounded still by the formidable walls of the head of the valley.

Walk uphill from the car park and pass an information plinth before crossing a stile. Walk along the right-hand side of the field towards the top right-hand corner and then bear left to continue along the fence to reach another stile.

Follow the broad but faint grassy track straight on. As it reaches steeper ground, it becomes a better-defined stony track that swings slightly left and climbs the hillside. Continue ahead, up towards the head of Cwm Gwdi, and keep ahead, ignoring a few right forks, until the path eventually levels out on Cefn Cwm Llwch.

Continue along the ridge towards the summit ahead. As you reach the foot of the peak, the track steepens considerably, offering a fine viewpoint over a perilous gully that drops into Cwm Sere on the left. Continue to climb steeply over a few rocky steps to reach the summit cairn on Pen y Fan.

Bear right to follow the escarpment edge along and drop into a shallow saddle eneath the rising crest of Corn Du. Fork right up on to this summit, then bear left for a few paces to locate a steep path that drops down through rocky outcrops on to easier ground below. Bear right and drop past the summit.

Continue down the hill forking right to pass the Tommy Jones obelisk with the steep crags of Craig Cwm Llwch on your right-hand side. Above the lake, the path forks; take the right-hand option and right again at the next fork to drop steeply, around a dog-leg and over moraine banks to the lake shore.

A clear track leads north from the lake - alongside the outflow; follow it over easy ground to cross a stile that leads on to a broad farm track. Take this down to a gate in front of a building and climb the stile on the left. Cross the compound and climb another stile to follow waymarker posts around to the right on to another track, beyond the building.

Bear left on to this track and follow it down, over a footbridge, to a parking area. Keep straight ahead, through a gate to a crossroads, where you turn right. Cross the bridge and continue for over a mile (1.6km) ignoring turning to left to another T-junction. Turn right and walk uphill back to the car park.