Last month, 21-year-old intern Moritz Erhardt died while nearing the end of a summer placement at an investment bank in the City of London. Reports suggested he had worked for three days and nights in the run-up to his death, and the incident has prompted a review of the working conditions for junior staff at the bank where he worked.

One former intern and junior banker who worked in the City of London spoke to Radio 4's The Report about his experience.

You hear questions in interviews about how hard do you work, are you willing to put in the hours, are you willing to stay late?

The answer we'd always look for when we were interviewing candidates was "as hard as is necessary".

But you only really understand what goes on when you get on to the desk and you sit there on your first day and you see the clock.

It's nine at night, and no-one has left. The clock hits 10, 11 and 12 and still everyone is there.

You are told you stay and you work until the work gets done.

But the problem there is that the work always keeps coming.

I ended up doing an all-nighter in my first week as an intern, which is when you start work at nine, you stay until five or six the next morning, you go home, have a quick shower and then head back into the office and continue working.

And I think the really bizarre thing about that is, as an intern, you're almost functionally useless to your desk. You're not really adding anything, you're not really doing anything, you're just one more warm body.

But because everyone else on the team is doing it, the expectation is that you are there and you are willing to be there at the same time even if all you are doing is looking over someone's shoulder.

I've lost count of the number of times I did that as an intern.

Within six months of starting, I was looking for another job because I knew that I couldn't keep it up.

Substance abuse

Alexandra Michel, professor of management and organisation at the University of Southern California Marshall School of Business, studied a cohort of bankers for nine years After four years, she observed that many of them who had worked 100-120 hours a week suffered from chronic back pain, auto-immune diseases and insomnia

Performance also suffered. While technical skills like doing complex sums were unaffected, she says creativity, judgement and ethical sensitivity declined after four years of working long hours

Prof Michel also identified problems with addiction, anxiety, depression and other health complaints that could not be diagnosed but were induced by stress

First of all, you can just roll with it, be incredibly sleep-deprived and function far below normal.

The second way is you can try and get what sleep you can and that involves stuff like finding a cubicle in the toilet and leaning against the wall and sleeping for 20 minutes there.

A friend had this technique of putting a book or some papers on her desk, putting her hands to either side of her head and then she would have her hair fall in front of her head.

You couldn't see that she was actually fast asleep.

And the third way, and one which is, I think, increasingly common, is you use a sort of substance to help you stay up.

Lots and lots of people, particularly Americans, will use Adderall, Ritalin and Modafinil.

Adderall and Ritalin are ADHD drugs and Modafinil is an anti-narcoleptic which basically shuts off your brain's desire to sleep.

The first two are prescription-only and I think people either have friends who have prescriptions and buy through them or, in the case of Modafinil, you can basically find a website and it will be shipped to you from East Asia.

I took Modafinil I'd say four to five times a week during busy periods.

It feels a bit like you have had a cup of coffee but without the jittery effects coffee gives you and you just stay quite steady, quite focused, quite alert.

You notice yourself become less functional mentally, so you can feel your abilities drop off but there's none of the tiredness which normally accompanies that.

I would just be a lot more prone to getting into verbal arguments with people, having a few fights with my girlfriend, and just a lot more defensive about everything I was doing.

Blackberry smashed

There was one evening where I said to the senior guy I was working under: "Look, I'm going out to dinner for an hour. This is the name of the restaurant. This is where my table is. It's for a family 50th birthday. I have to be there and I'm coming straight back."

During dinner I started getting angry emails on my Blackberry saying, "Where are you? Come back to the office now."

I went back and the guy was so angry that I'd stepped out that he hurled a Blackberry across the room.

It hit a glass wall and smashed.

A few of the mid-level guys took me aside and said: "He's not very happy. You need to up your game a bit. You need to be more available."

In these sorts of places you get a reputation if you're not happy and willing and accessible.

The banker spoke to The Report's Phil Kemp.

You can hear more about his story and others like him in The Report: Sleepless in the City on Radio 4 at 20:00 on Thursday 12 September.