Louis Theroux marks 25 years in the industry this month - and he's undergone quite transformation.

Since making his TV debut in the 90s, the documentary-maker has amassed a cult following of fans who are besotted with his 'nerdy' persona.

However, during an appearance on the Lorraine Kelly show to discuss his illustrious career today, it appears the father-of-three could shake off his geek chic tag to start marketing himself as a bona fide hunk.

During his video call with Lorraine, 50-year-old Louis was happy to roll up his sleeves and flaunt the bulging biceps he was struggling to conceal under his navy t-shirt.

Lorraine Kelly was astonished as Louis Theroux flashed his bulging biceps at her

As he showed off his impressive physique, Louis admitted to Lorraine that the change had come after he discovered the sweaty joys of Joe Wicks' workouts during lockdown.

"It's not about muscles, it's about mental health, but muscles are a by-product," he informed Lorraine as he gave a flex of his chiselled arms.

Lorraine looked suitably impressed as she sat back mouth agape at his his efforts.

But despite his hardened physique, Louis was keen to stress he has not forgotten his nerdy roots that brought him his legions of fans in the first place.

Louis Theroux has won legions of fans for his 'nerdy ways'
Louis was happy to strip off for his art - pictured here getting naked for a porn shoot

Louis admitted to Lorraine that his 'nerdiness and awkwardness' were integral to his success.

"I wish I could claim that my geekiness was a quality I had to work on, it seemed to come quite naturally to me, at the beginning I didn't realise that it could be an asset," said Louis, who said his sheepishness helped interviewees open up to him.

"I plead guilty to still being a bit of a nerd," he added.

Louis was asked to appear on Celebrity Bake Off
The star walks the red carpet with wife Nancy Strang last year

After starting his career as a newspaper journalist, Louis got his big break with the BBC and Louis Theroux's Weird Weekends.

Fans quickly fell in love with Louis' perpetually deadpan demeanour as he mingled with a variety of subcultures from porn stars to white supremacists.

Louis' fanbase continued to expand as he landed 2000 series When Louis Met... that saw him spend time with a number of celebrities.

Unlike his peers, Louis refused to act any different around high profile stars including Michael Jackson and Jimmy Saville as he delved into their daily lives.

His unique style paid off as When Louis Met Jimmy went on to be voted one of the top documentaries of all time in a 2005 survey by Channel 4.

When Louis Met Jimmy was voted one of the top documentaries of all time

While Louis' presenting style has rarely veered of course, his style has undergone quite the evolution.

After adopting a nonchalant attitude to being on camera with his rimless glasses, unkempt hair and even wearing the same shirt throughout an entire TV series, Louis has gone full on geek-chic in recent years.

These days Louis' is recognisable for his salt and pepper hair, rugged beard and feature spectacles.

The change has not gone unnoticed with Louis being once named the seventh most wanted man in Britain by high society magazine Tatler.

He's also made the top ten of Heat Magazine's 'Weird Crush' list on numerous occassions.

The fan girling has reached Louis' attention with women stripping off at his book singings and asking him to sign their bare breasts.

Louis Theroux poses with his BAFTA Award in 2019
Louis interviews Christine and Neil Hamilton in 2001

Recalling the shocking experience in his own unique way, Louis shared: "Well, I was once signing books in Oxford and two fans came and got their books signed. And then they took their tops off and they were topless. They said, 'we want you to sign our breasts now'.

"This was in 2005, and to my slight shame, I was a bit embarrassed and I thought that my being embarrassed made them feel embarrassed.

"Really I would just like to say thank [to those two women] for doing that because it probably took some courage and there’s no harm in that,"he said.

Louis Theroux 'fan merch' now includes items such as t-shirts, posters, mugs, badges and even scented candles as the hysteria refuses around the Bafta-award winning star reaches new levels.

While 17 Louis obsessives have also had his face permanently tattooed on their bodies.

Louis will star in a new show celebrating his 25 years in the industry

His latest project is certainly one for his band of loyal followers.

BBC Two series: Louis Theroux: Life on the Edge looks back at Louis' 25 years of documentary making.

Four, hour long episodes will see louis recount some of his most memorable interviews.

Speaking of why his love for the job has never diminished, Louis explained he never loses interest: "It's the nature of the work I do that i meet people whose beliefs are different, and sometimes totally abhorrent, including neo-nazis, racists, even paedophiles."