Here, he tells The Sun about the jobs that really put a spanner in the works and reveals the most common mistake everyone makes.

Serial killer fears

One job at a run down flat in North London had all the makings of a horror movie.

Upon entering the home, Nick quickly noted a foul stench, an axe and chainsaw kept in plain sight, and a pentagon on the bathroom wall.

The client was a thin man with yellow teeth and a soulless expression in his eyes, and appeared to have not left his home in weeks.

Briefly stepping out to call his wife Jo, Nick made sure to give her the location of his address, but went back in to fix the client's broken toilet.

The breaking point came when the plumber heard the front door lock, before the man asked him to pop down to his dark cellar to check the water supply.

Nick came up with the excuse of grabbing some equipment from his van and made a hasty escape.

"My wife and I were watching a lot of programmes about serial killers so it affects you," Nick says.

"There's no doubt about it that the guy was very creepy and the situation did scare me.

"The place had no electricity and it was full of rats and rubbish. I don't think he was a killer but I'll never know. I didn't like the way he locked me in. You never know who you'll be working for until you get there."

Sex blunder

One of the most uncomfortable moments in Nick's career came when a young lad thought he was home alone.

Nick explains: "I got in quite early in the morning to start work and his mother said she had to go to work so I should help myself to tea or coffee and that her son was in from uni.

"I was putting a new kitchen tap in for her and had to fix a toilet upstairs. And of course, as soon as she left, it turned out he had got his girlfriend in upstairs and there was a bit of sh***ing going on.

"And it's really difficult to know what to do in that situation. Do you tell him you’re there or do you let him carry on and just keep yourself to yourself?"

After thinking they had finally had enough, Nick carefully made his way upstairs to start the job in the toilet - but was amazed when the couple started going at it again.

Then, he heard the girl announce that she needed a wee and heard her approaching the bathroom.

Nick explains in the book: "‘Don’t move, I’ll be right back,’ I heard her say, as she tried to push the bathroom door open with her foot.
"‘It’s all fixed,’ I said, unbolting the door. ‘I’ve put a new
kitchen tap in for you downstairs as well.’

"She was draped in his dressing gown, had clearly been sweating and her hair was dishevelled.

"She looked at me with absolute horror, turned round and ran straight back into the bedroom. ‘You told me there was no one in the house, you bastard!’ she screamed, as I quickly flushed the loo, to check it wasn’t leaking, gathered my tools and left."

Common mistakes

Clearing stomach-churning drains is part of a plumber's day-to-day life, but some really do leave a mark.

Nick explains: "There's one moment where I actually pulled a live rat out of a drain. It got stuck in the U-bend underneath and it was horrible."

When it comes to common mistakes that lead to blockages, he says sanitary products are often unwisely flushed down the loo.

He adds: "I've come loads of tampons, but the worst is when you get a fatberg.

"That's when a kitchen sink goes straight out into a drain and there's loads of grease in it.

"It's the combination of that and washing powder. It's not very pleasant."

Appy days

In the book, Nick explains how he often gets a "flurry of activity" from clients for no apparent reason.

On one occasion, he realised this was due to his business being bizarrely advertised on the gay dating app Grindr.

During the build-up to the London Olympics in 2012, he worked for a gay man who ended up undercharging him as he was "feeling generous".

"After I finished the job, for about a week, I was inundated with lots of calls from the LGBTQ community," Nick recalls.

"I assumed this guy had just recommended me to all of his friends and he had lots of friends. My business is all word of mouth.

"At one point someone came up to me and said you know you're being recommended on Grindr and I didn't even know what that was.

"I later found what it was and it was so funny."

Botox pioneer

Nick also recalls the time he inadvertently built what become one of London's first-ever Botox studios for a divorced client with an incredible mansion.

"It was around 2005 or 2006 and I didn't know what Botox was at that time - I never heard of it," he says.

"But this woman was ahead of the game on it. I literally went to unblock her bog and then I ended up building her two bathrooms and a Botox studio.

"We built the Botox studio first and when we were there, all these women kept turning up - there were loads of them.

"I had a team of guys working with me and we couldn't work out what was going on. These middle-aged women would turn up and disappear into this studio.

"We had no idea about what we had built. They'd all come out wearing big hats and large sunglasses and disappear. 

"I think she's sold it now and it was so interesting. You never expect to come into contact with that but we did and I thought it was fascinating."

'Ying and yang'

Nick's adorable and hilarious relationship with his wife Jo and their two children is also discussed in the book.

Jo is his accountant and often gets frustrated by his lack of organisation skills when it comes to paperwork.

Nick says: "We're ying and yang. She does an incredible amount of paperwork and she's very big on it - and I'm a plumber. I fix things.