Ultra running: Running the length of New Zealand – that's a thing to Bragg about

The recorded message on Jez Bragg's mobile phone says he is on an "extended sabbatical". But that doesn't tell a fraction of what the British ultra-runner has been up to over the last couple of months.

He has broken a record, for a start, for the fastest traverse of the 3,000km (1,864-mile) Te Araroa trail, which runs the length of New Zealand.

Even the bare numbers – 53 days of running an average of 35 miles daily – sells Bragg's achievement short. Factor in that he ran over mountain ranges, through shoulder-high grass and knee-deep mud – plus 80 miles of kayaking – and you begin to get a picture of what he did.

Then there was the giardia, an intestinal parasite he contracted in a remote part of South Island on day 37. It floored him for three days with excruciating stomach pains, vomiting and diarrhoea.

"To be perfectly honest, I thought [it was over] then," he told the Talk Ultra podcast hours after finishing in the southern town of Bluff. "I was in a really bad way for three full days and for several days afterwards I was not back to full strength. To go from running 16 to 18-hour days to being horizontal for three days was bizarre in itself. It just made me feel so low. I had gone to almost like an old man who was bedridden, weak and helpless.

"I remained determined to try and get going again but there was a nagging doubt, of how I can ever get back strong enough to run 60 or 70 kilometres a day again. There were all sorts of things going through my head. The fourth day after being struck down, I thought, 'Right, I want to do something', and I walked four kilometres down the trail with two sticks and I literally couldn't go any further. I had to stop and try again. The next day it was 20 kilometres, then the following one I managed 40, over some really tough terrain."

Bragg, who ditched healthy breakfasts early in the expedition in favour of fry-ups, to ingest enough energy, did finish, three days over his original target of 50 days. And even with the high-calorie diet, the figure that held the Union Jack aloft in Bluff last Sunday was noticeably thinner – with a full-face wildman beard – than the one who set off in the far north of New Zealand on 12 December.

Bragg, who was given the chance to tackle the route through his sponsors The North Face, said the run changed him mentally too. "It was harder than I had ever imagined," he said. "There were so many things thrown at me, it has been incredibly hard to deal with. It has solidified me physically and mentally, knowing I can push myself through some really horrible lows.

"I know it will change me, for sure. It has stripped away my daily life and revealed my core emotions. I really hope to retain that, because it illustrates what is important in my life and now I know that. It has cleansed me.

"It has been the ultimate break and has given me the chance to clear myself out. I will probably be more relaxed – I am not sure how I will settle back down to commuting to London for work, though."

For the full interview go to iancorless.com