The problem was that the mezzanine didn't play a big part in the life of the flat; it was sometimes used as an office space, or as a place for overnight guests to sleep. Then a pal turned up needing somewhere to stay for more than just a single night.
"There was nowhere else for him to go but in the mezzanine," says Richard, 30. "My girlfriend and I used the main bedroom so that was that."
Richard works in publishing so, understandably, another function of the mezzanine had been as a place to store books that had spilled over from the piles in the living room.
Even with the books dealt with, the mezzanine was an open space, so not ideal for a bedroom.
"Basically, as soon as we were up making breakfast in the kitchen, it meant the whole flat was up," says Richard.
As their guest became a long-term resident, Richard reconsidered how the flat was laid out. "It's not huge in terms of square feet but because it's a converted classroom, the rooms are really high. I knew the only chance of increasing the space was by using that height."
Richard consulted Chris Bryant, partner at architects Alma-nac, and together they came up with a plan.
'Now I love this flat even more. It's amazing how it's been so radically changed by something so simple and cheap'
Says Chris: "The brief was for adapting the mezzanine for use as a second bedroom but with the option of returning it to a study and working space later. The answer was to close in the space and turn the mezzanine into a room with a set of folding timber shutters.
"The shutters provide separation from the main living space, while maintaining the option for an open, bright, communal space when the room's not in use as a bedroom."
The ingenious design, which cost £12,000, involved building a full-height wall up the side of the staircase leading to the mezzanine.
In this wall, Chris designed built-in wardrobes, a sliding "bedroom" door so the room can be closed off completely and, of course, two bookshelves. There is even a little recessed light that pulls out of the wall to become a bedside table and lamp.
"With space being tight, the sliding entrance to the bedroom doubles up as the closing mechanism for the hanging storage," says Chris.
The pièce de résistance, however, is the concertina shutter, made of oak, which fits into the "window" space on top of the existing waist-high wall.
When closed, it efficiently blocks out the light, is noise-proof and makes the space private. In a nice touch, when the shutters are folded back, they resemble a giant book end.
Richard also had a full-height bookshelf built at the end of the living room, lending the apartment a great sense of theme and harmony. He loves the results and can see the value the project has added to the property. "Before, we just had a large white wall with an opening in it. Now we have a second bedroom but also the shutters open or closed look like a giant piece of ever-evolving artwork.
"The flat has been completely transformed and the funny thing is I probably would never have thought of doing the conversion if our friend hadn't come to stay."
For a comparatively small amount of money, it has turned what was essentially a luxury bachelor pad into a proper two-bedroom flat, which could be sold as such.
"I have always loved this flat and now I love it even more," says Richard. "It's amazing how it's been so radically changed by something so simple and relatively cheap. It just shows what can be done with a little imagination."