The PHD M.Degree 400k sleeping bag appeared on our guide to the Best sleeping bag for hiking. PHD makes all of its sleeping bags from start to finish in a UK factory. The company sources more than 95% of materials and components within Europe and minimises global transportation. The down is ethically sourced by PHD itself. This goes some way to explain the fairly eye-watering price of the PHD M.Degree 400 K custom-made, but it’s also a fully custom-made bag. As such, it fits me like a glove in width, length and at my feet.

Price: £882 | Weight: 560g (Standard Custom Made) Materials: 1000 fill power European goose down; shell and liner: 7X ripstop nylon with DWR | Temperature: comfort -9C | Features: Customised to suit customer size and needs; choice of four lengths and four widths; half and full-length zip, right or left, dual-construction design, oval-shaped footbox, various add-on options at extra cost including waterproof footbox/outer shell, stuff bag, mesh storage bag | Sizes: 16 sizes, depending on requests | Men’s version: Unisex

Slipping inside the bag is immediately cosy, and it’s easily the warmest bag I’ve tested. It’s also the lightest, and to achieve this PHD uses a different construction on the top compared to the underside to “optimise down lofting and shed excess bulk”. Weight is further reduced by the lightweight and wind-resistant nylon lining and shell fabric. I also chose a short zip.

The hood is smaller and more basic than other bags, and whilst it can be cinched around the neck it doesn’t have baffles. A couple of niggles include a sticky zip, and a drawcord for the hood adjuster that sits annoyingly in front of the face. Additionally, the narrow fit means stretching my legs whilst sleeping is not possible. PHD custom-made bags are for those who demand the best warmth-to-weight ratio, and who are prepared to pay for it.