Christmas is not a season known for taking prisoners. It's no wonder that by the time we drag our ever-widening bodies into the new year, the only resolution we want to make is to start a Facebook group calling for December to be outlawed, or at the very least towed into the North Sea and scuttled. However, all is not lost. Look out of the window now and, with any luck, you'll see one of those clear winter days that Britain does really well. The woods have long since dissolved into shades of soft brown sugars; the sky is a gorgeous cerulean; and wild animals skitter about leaving tiny footprints in the crisp crust of frost. Could there be a better way of kicking the year into action, getting those endorphins flowing, and giving yourself a well earned detox than getting out there and climbing a mountain? Well, yes there is: you could go out and climb a Marilyn.

Unless you are one of the growing number of "Marilyn baggers", you could be excused for wondering what a Marilyn has over the UK's more commonplace bulges. The answer is simple: Marilyns stick up at least 150m (about 500ft) above everything around them. This not only guarantees a decent hike up, but also means you'll enjoy an uninterrupted view when you get to the top. Furthermore, having a go at a Marilyn can take you beyond the well-worn paths up worn-out hills, thus allowing the usual suspects such as the Lake and Peak Districts, Snowdonia and the Cairngorms a much needed breather.

So how do you work out which hills are just hills and which ones are prized Marilyns? Happily, there is a list. It was compiled by Alan Dawson, a former cartographer from Liverpool, who came up with the Marilyn concept and wrote a book to let everyone know where they all are. In a refreshing show of altruism, the entire text - including the all important list - can be found on his website (see below), making locating a Marilyn in your region, or one you plan to visit, a simple affair. Oh, and in case you're wondering, the name is a subtle joke: Scottish hills higher than 3,000ft are called Munros.

Head for England's most northerly Marilyn, the Cheviot (815m), and you'll find laid on for you a base camp sans pareil in the magnificent Deer Hut at Barrowburn. A rare example of an Edwardian prefab, the "hut" is actually a cosy wooden bungalow high up in Northumberland's remote Coquet Valley. With an open fire, gas lighting (the national grid grinds to a halt six miles away), water piped straight from a spring and no mobile phone reception, all you need are some retro walking boots and a stout duffle-coat and you can star in your own John Buchan novel.

However, for our first night, my girlfriend and I tried out the camping barn next door. Originally built as a schoolhouse at the behest of a Mr Blythe - a one-armed Gypsy from the family that was to bring forth Bill Clinton - it has been restored by local farmer Ian Tait, once a pupil at the school and, incidentally, one of the nicest people on the planet.

I've spent many an unpleasant night freezing half to death in camping barns, huddled painfully over my gas stove, so I was a little apprehensive about spending the night here with the temperature plummeting outside. This, however, is no ordinary camping barn. We were greeted by a roaring fire, a well-equipped kitchen and two minstrels' galleries serving as sleeping platforms, and proceeded to spend as snug a night as can be.

It's a cobweb-banishing, limb-warming day's walking from Barrowburn to the Cheviot's striking tabletop summit. En route, we took in the aptly named Windy Gyle before joining the Pennine Way, which here snakes along the Scottish border. These hills were once ruled by the Reivers, raiders for whom robbery and murder were a lifestyle choice, and it's easy to imagine what apprehension a shepherd boy on look-out duty might have felt as he scanned the countryside. But what countryside: not only could we see deep into Scotland (almost to Edinburgh on a clear day, it is claimed) but as far south as the Lake District too.

Just one word of warning: Marilyn bagging can become addictive, and you could soon find yourself thirsting to attempt all 1,554 of them. Should this be the case, you might find two of them a tad more challenging than the rest - unless that it is, you're already in the habit of climbing vertical sea stacks off the Atlantic-ravaged islands of St Kilda. The other 1,552, Dawson maintains, are somewhat less taxing.

Four Marilyns to get you started

Leith Hill, nr Dorking, Surrey
Map: OS Landranger 187 - TQ 139 431

Not only is this the highest summit in south-east England, it's also topped off by an 18th-century gothic folly built to take the hill above 1,000ft. Weather permitting, you can see St Paul's Cathedral, the English Channel and an astonishing 13 counties from the battlements. Down below, there are nature trails and a seat made by sculptor Walter Bailey. The tower is open at weekends (National Trust, adults £1, children 50p).

· Where to stay: The Inn on the Green, Ockley (01306 711032, inn-onthegreen.co.uk) a 15th-century country pub with a highly praised restaurant, doubles £65.

Holyhead Mountain, Anglesey
OS Landranger 114 - SH 218 829

Holyhead is best known as the rather dreary jumping off point for ferries to Ireland, but its mountain is well worth venturing up. Set in a country park, it affords splendid views of the Irish Sea. Look out too for the 50 mosaics recently created by local schoolchildren and dotted around the landscape.

· Where to stay: The Beach Hut, Holyhead (01407 764001, thebeachhut.me.uk) a funky seaside guesthouse, £25pp pn.

Titterstone Clee Hill, Shropshire
OS Landranger 137/138 - SO 592 779

In an Area of Outstanding Natural Beauty, Clee Hill lowers menacingly over Ludlow. It's the site of a number of defunct dolerite quarries which give it an unsettling lunar feel. There's also a bronze age cairn, an Iron Age hill fort and a radar station up there to add to the spooky atmosphere.

· Where to stay: The Clive Bar and Restaurant with Rooms, Bromfield (01584 856565, theclive.co.uk). Snappy name, even snappier place, doubles from £85.

Arthur's Seat, Edinburgh
OS Landranger 66 - NT 275 729

Proof that you don't have to leave town to bag a Marilyn. Arthur's Seat famously dominates the Scottish capital and makes for a satisfying quick escape when the hustle and bustle of Auld Reekie gets too much.

· Where to stay: The Glasshouse, Edinburgh (0131-525 8200, theetoncollection.com). Ultra-swish former church with (so they claim) the only rooftop garden in the city (rooms from £105).

Way to go

Barrowburn (01669 621176, barrowburn.com): the Deer Hut (sleeps 4-6) £60 per night; the Camping Barn (sleeps 1-17) £10pp or £80 for exclusive use. GNER (08457 225225) London-Alnmouth from £26.

The Relative Hills of Britain by Alan Dawson (Cicerone Press, £9.99) and bubl.ac.uk/org/tacit/marilyns/index.html.

· Dixe Wills is the author of Places to Hide in England, Scotland and Wales (Icon Books, £7.99).