A geometric wall mural and a berry-toned bedroom appear inside this central London penthouse, which has been created by fashion designer Roksanda Ilincic.

Reflecting her penchant for bold colours and shapes, Roksanda Ilincic says the three-level apartment "talks to my brand DNA and is the voice of my collections, but is still something different".

"It was interesting that somehow the final result was very similar to what I do in my ready-to-wear. I think that's the beauty of it," Ilincic told Dezeen.

The apartment is set inside one of three 19th-century gas holders that WilkinsonEyre and Jonathan Tuckey Design converted into luxury residences early last year.

Host to 145 apartments and 9 penthouses, the cylindrical blocks are just a stone's throw from other recent King's Cross developments like the Heatherwick-designed shopping complex Coal Drops Yard.

The focal point of the Roksanda-designed apartment is a huge geometric mural in the dining area, hand-painted by Swiss artist Caroline Denervaud. Featuring blush-pink, sandy beige and navy blue forms, the wall provides a warm backdrop to the room's pale marble table and breakfast island.

Simple white cabinetry and brass hardware have been incorporated in the adjacent kitchen.

"I wanted to create a dream space that doesn't necessarily feel like a dining room, somewhere where you want to dive in and spend a long time," said Ilincic.

Another piece by Denervaud can be seen in the living room, attached to the wall with simple gold bulldog clips.

Other than a couple of bright-yellow fibreglass chairs, the colour palette here is kept neutral with a curved white sofa, floor-to-ceiling timber bookshelf and perforated cane seats by Swiss architect Pierre Jeanneret.

Pale pink Kvadrat curtains hung in front of the full-height windows lend the space a rose-tinted hue.

A short flight of stairs leads down to the sleeping quarters. The master bedroom features a burgundy-framed bed by Italian architect Tobia Scarpa, as well as a spherical floor lamp by New York-based designer Eny Lee Parker.

Ilincic has included furnishings, books and decorative ornaments from her favourite selection of female creatives throughout the apartment, all of which can be purchased with the property.

"Art and architecture are always my starting point, and also women – empowering women, sheltering women, highlighting femininity, strength…all the differences we carry within ourselves," she explained.

At this level there is also a study, anchored by an ovular Charlotte Perriand table, and a cosy reading nook. Dressed with a single tan leather chair by Brazilian-Italian architect Lina Bo Bardi, the space looks through to the apartment's central lightwell.

"It is really a place to think and to reflect – I think that's something we miss in our lives, so it's really an ultimate luxury. It has a certain tranquility," Ilincic added.

Steps on the floor above also provide access to a private roof terrace, which overlooks the London skyline.

Serbia-born Ilincic studied architecture and design at the University of Arts in Belgrade before earning a master's degree in womenswear from London's Central Saint Martins.

Keen to add to her already multi-disciplinary background, the fashion designer thinks she will take on more interiors projects in the future.

"I'm a person that likes to do many different things, obviously I'm doing fashion but I always find a reason to collaborate with artists. These things give me more food for thought, my brain likes to works across different categories," she said.

"I think there's a really big crossover – the way you approach [fashion and interiors] is the same. You start with your inner feelings, the instinct that you have, and the knowledge that you've picked up along the way."

Ilincic isn't the only fashion designer to have turned their hand to interiors – at the end of last year, Bella Freud completed the fit-out of an apartment inside London's BBC Television Centre.

Featuring glossy furnishings, cherry-red walls and emerald-green carpentry, the space is intended to evoke the "bold colour, eclecticism and glamour" of the 1970s.

Photography is by Michael Sinclair.