THE rain swept across the deep void of Coire Sputan Dearg like curtains being drawn, and I knew that I only had seconds to get my waterproofs on.
Beyond the silvery veil the late afternoon sun was highlighting the rocky features of Cairn Toul, shining through a morass of thunderhead clouds that looked like some mass eruption of boiling vapour.
Despite the incipient soaking, I was transfixed by the splendour of it all.
Showers had swept across the Cairngorms all day and in between the sun, shining through great rents in the cloud cover, had deepened the earth tones of late summer and picked out individual features with crystal clarity.
Lochan Uaine, one of four green lochans in the Cairngorms, suddenly changed in colour from quicksilver to translucent blue; patches of blue moss campion shone from the metallic greys of the scree-covered slopes, and away below me sunbeams swept across the pines of Glen Luibeg like a roving searchlight.
Despite the rain these are the best of days in the Cairngorms, when light and shade contrast sharply and the colours change constantly.
I had chosen a marvellous route to enjoy the spectacle of it all - a tour of the central massif of the Cairngorms.
The route starts at Linn of Dee, near Braemar; visits the pine-scented and deer-haunted Glen Luibeg; climbs the long Sron Riach shoulder of Beinn Macdui to its spacious summit; touches the edge of the crags and cliffs of Coire Sputan Dearg and visits the spectacular Arctic setting of Loch Etchachan, before heading off down the long ridge of Derry Cairngorm.
It's a big day, not far short of 20 miles, but that distance can be effectively reduced by using a mountain bike to carry you up the four bulldozed miles from Linn of Dee to Derry Lodge.
The Sron Riach ridge of Ben Macdhui, the brindled nose, climbs steadily all the way to its conical peak.
Beyond, there's a brief descent then another climb on to the bare, wind-scoured east slopes of Macdhui, Britain's second highest summit. Wide, empty slopes lead to the conical summit past the ruins of the Sappers' Bothy (for many years the armed forces delighted in building stone shelters and huts all over these slopes).
From the summit cairn the views, on a clear day, are superb, but there's still a long way to go. Head back down to the edge of Coire Sputain Dearg and try and stay with the cliff rim.
In many ways this is the highlight of the route, a grand esplanade with Coire Sputain Dearg dropping away below you on one side, sweeping down ochreous miles to the verdant green of the Luibeg pines, and the Arctic splendour of Coire Etchachan on the other side with the most magnificent loch in the Cairngorm filling its rocky bowl.
The tor-studded whaleback of Beinn Mheadhoin looms beyond the loch and away across the deep chasm that holds Loch Avon rises Cairn Gorm itself, its glaciated cliffs forming an acute angle with the gentler swells of its summit slopes.
From the shallow col below Creagan a' Choire Etchachan, the long ridge of Derry Cairngorm forms a highway to the south, dropping first to another, grassy, col before rising in slopes of scree and boulders to the rocky summit, yet another magnificent viewpoint.
To the east the green and brown sweep of the Moine Bhealaidh flows onto the rounded slopes of Beinn a' Bhuird and the empty miles of the Forest of Glenavon.
It's all downhill now, but it's a rocky course that demands considerable attention before you can begin to relax.
The broad ridge runs south before sweeping to the south-west towards Glen Luibeg and a gentle wander beside the burn back to Derry Lodge.
