We start walking in drizzly mist on a sketchy forecast, but there’s no going back now. The beech forest is beautifully uniform, dark and foreboding. We follow Rough Creek, which fortunately doesn’t live up to its name, then veer steeply upward.

The bush line appears suddenly, and we emerge onto the rolling, tussocky tops where we get that heart-lifting feeling – no longer confined by the dark forest, views in all directions and quick travel in front of us. The afternoon sun is peeping through and the tussocks range in hue from straw to gold and rich red. Gentians, Mt Cook lilies and mountain daisies are blooming, and tiny tarns punctuate the landscape.

It’s a fun romp across the basin to the ridge overlooking Lake Christabel.

The boomerang-shaped lake lies behind a landslide dam, thought to have been created by a prehistoric earthquake, and is the largest New Zealand lake not colonised by introduced fish. Long-finned eels and koaro (whitebait), renowned for their ability to climb waterfalls, have penetrated the underground outlet, and the lake is protected as an ecological reserve.

Our bunks for the night are in Lake Christabel Hut, sited on a clearing by the Blue Grey River a couple of kilometres short of the lake itself. Robins and pīwakawaka keep us company as we drink tea in the sun outside the hut.

Our next day involves crossing the main divide from Lake Christabel to the Nina Valley. We have two options. The first: to follow the track leading towards the Robinson River then cross Boscawen Saddle and descend into the upper Nina. The second: to climb directly to the tops south of Lake Christabel Hut, sidle through a saddle and follow a rib down into the Nina. The second option looks more direct. We scour the hut book to see what routes other parties are taking. Only a few groups are heading to the Nina, and all of them via Boscawen Saddle. Perversely, we decide to take the other route.

It begins well through reasonably open, untracked bush. Soon it gets very steep, and we are grabbing hold of slender beech trunks, hauling ourselves up. At least the threatening rain has retreated. We navigate round a bluffy section, and after 700m of ascent we hit the horrendous scrub band. Progress is infinitesimally slow, but eventually we make it through and find ourselves on a steep rocky slope with Pt1648 above us and the saddle we need to the east. The sidle is steep and difficult, and we do some unnecessary climbing up and down before having an early but well-deserved lunch on the broad saddle flanked by imposing rock sentinels.

The route into the upper Nina is obvious. We enjoy more tussocky tops travel before we hit the bushline, and travel down the upper Nina is fun and splashy.

The two-bunk Upper Nina Bivouac has been newly renovated and is used as a base for Hurunui College Valley Restoration Group. Established in 2008, the group has trapped over 1000 stoats and rats and introduced great spotted kiwi to the area.

It was tempting to overnight in this impossibly cute biv, but we needed to put in more kilometres if we were to make it out of the hills for Christmas Day. We kept going, sloshing along the boggy track, impressed by the number of traps. Our long day finished at the newish 10-bunk Nina Hut, which is perched about 70m above the river on a knoll in a parkland of moss glades and beech trees.

The route now took us over another range into the Doubtful River. We left early in a cold, foggy drizzle and sidled through beech forest high above the Nina then climbed steeply to Devilskin Saddle. To our surprise, Devils Den Bivvy, 100m above the saddle, had been occupied the night before. ‘Two-person biv, my arse,’ read the hut book, ‘we slept four in here.’ These guys were in front of us, and they were heading to Lake Man Bivvy, our planned stop for the night. Damn! With no tent, we’d have to stay in one of the huts in the Doubtful River valley, meaning some very long days after that.

We pushed our way through waist-high red tussock down to Devilskin Stream and the bushline, then followed high above the stream as we descended into the Doubtful River Valley. The silver beech forest was beautiful but there were numerous windfalls.

Doubtful Valley boasts two huts: Doubtful, and the jokingly named Doubtless. We’d both caught hut-bagging fever in an increasingly serious way, but as Lake Man Bivvy wasn’t available to us, our consolation was to walk further up the valley to Doubtless Hut.

It was full of steaming bodies and mounds of gear. “You guys said you’d be at Lake Man Biv!” I exclaimed, before regaining a more friendly demeanour. After a hot drink and some chat, we decided to retrace our steps down the valley and climb up to Lake Man Biv, as the party in Doubtless Hut had decided to leave the biv to the following day.

It was late afternoon as we clambered onto the Doubtful Range then sidled above the Kedron River. The 500m climb was harder at this time of day, and we were well ready for our soup by the time we sighted the cheerful little biv. Stunted beech and expanses of luxuriant emerald moss surrounded it, and a merry stream was the water source. A pickaxe hung on a wire loop at the corner of the hut for  digging toileting holes as there was no thunderbox.

A side trip to Lake Man would have been the icing on the cake the following day, but our Christmas date beckoned. Setting off over yet more rolling tussock tops, we enjoyed the sweeping views back to the Doubtful and ahead to the Hope River Valley. Marker poles led us to a steep, narrow ridge, which we followed all the way down to reach the middle tributary of Pussy Stream. Following this brought us to the expansive grassy flats of the Hope Valley.

This is hutbaggers heaven. We did a detour up-valley to bag Top Hope Hut, then returned to St Jacobs Hut for a rest in the shade. It felt amazing to have this tranquil parkland of meadows fringed by beautiful red beech forest all to ourselves. The hard travel done, we enjoyed the easy walk down-valley to Hope Kiwi Lodge. Corralled by a wire and timber fence, it was built in the 70s and boasts red lino tiles, groovy timber panelling, several rooms and porches at the front and the back.

Our final half day was a straightforward trek down the Hope River Valley back to SH7, where we hitched a ride to Boyle Lodge with Harry, who greeted us with beers from his ute’s fridge.

Now here’s a thought. You’ve heard of the three-pass and five-pass trips: why not add this gorgeous four-pass trip to your to-do list of classic South Island routes? It’s certainly worthy of being crowned a classic, with a crossing of the Main Divide, beautiful rolling tops, spectacular beech forest, gnarly stream travel, clear green rivers, lush grass flats and cosy huts.