Intrigued, I called Helen Roberts, Head Designer at Rab and the lady who designs all their women's stuff. It's early, she's not had her coffee yet, neither have I and she knows a lot more long scientific words than me but the upshot is:

"The Vapour-rise series has developed a cult following because there is nothing like it on the market and it is very good at what it does: keeping you comfortable in a wide range of outdoor environments."

Vapour-rise jackets have a unique combination of Pertex Equilibrium outer shell and a special lightweight micro-fleece interior, Helen tells me. The fleece liner moves moisture away from the skin very effectively and the Equilibrium has a denier gradient which, in turn, passes the moisture through the outer fabric and disperses it on the outside. Because the outer fabric is quite, but not completely, wind resistant the whole garment is very breathable.

"...While I didn't intend to wear the jacket in some of the situations Rolfe has (“Alaskan, Yukon and Arctic summers can see bugs so thick in the air inhaling is made difficult. All of the Vapour-rise range is mosquito proof”) I was fairly sure I could give it a good testing and see what it was really made of..."

Apparently Vapour-rise was originally designed to be worn next to the skin and it works really, really well like this but most people layer it up with a light base-layer underneath. Helen herself finds that it is what she puts on to go out on most occasions no matter what she's doing: walking, climbing or mountaineering. Another one who lives in a Rab Vapour-rise! It sounded like putting the thing on was going to be a bit of a life-changing experience!

While I didn't intend to wear the jacket in some of the situations Rolfe has (“Alaskan, Yukon and Arctic summers can see bugs so thick in the air inhaling is made difficult. All of the Vapour-rise range is mosquito proof”) I was fairly sure I could give it a good testing and see what it was really made of. First off, I took it to the windy capital city of God's own rock: Stanage (Plantation) for some bouldering. I wore it over a light base layer and microfleece. True to its word, I was warm and comfortable as I walked up through the trees, and stayed warm and comfortable as I sat on the mat, wedged my shoes on and indulged in some early morning off-sighting (watching other people work out hard sequences and then not trying them yourself).

Although fitted, the jacket turned out to be stretchy enough to climb in so I left it on all day - pushing the sleeves up and securing them out of the way with the Velcro. It didn't feel at all bulky or restricting and held up to a bit of grit scraping, although I expect Duct tape detailing would be the result of repeated grit abuse. It rained a tiny bit towards the end of the day but the drizzle just beaded up on the jacket and rolled off so I didn't bother getting my hard shell out.

The next morning, I did what Helen had advised: take it for a run somewhere cold and windy and wear it next to the skin. So I zipped it on with some old leggings, put my car key in the zipped chest pocket and headed to Burbage for a run up Higgar Tor. It's pretty windy up there at the best of times but the jacket coped really well at blocking the wind without making me overheat.

At the top, I sat on the rocks to get my breath back. The hood stows completely away when you don't want it, and unravels to fleece-lined, easily adjustable brilliance with one of those Rab bendy peak things when you do. I pulled the hood on, put my hands in the hip pockets and marveled at the fact that I was just the right temperature.

I kept the VR on while driving home and thought about its genius: like a soft shell, but softer, like a fleece but warmer. Reasonably waterproof but more breathable and stretchy than a hard shell.

I've worn the VR continuously over the past week and it really is the jacket of choice for most conditions. Its beauty lies in its two perfect balances: firstly between wind resistance, waterproofing and breathability, and secondly between softness, warmth and weight. It keeps you warm but not sweaty and is light and unrestricting.

I've not taken this jacket out in winter conditions yet but the following letter was sent to Rab by someone who has:

Rab Vapour-rise Trail Jacket

• Weight: 440g
• Wind resistant/breathable Pertex Equilibrium ® outer
• Water repellent shield treatment
• Full length double slider zip
• 3 outer pockets
• Adjustable cuffs
• Rollaway hood secures to collar with zip and velcro

“I was just writing to say that I really love my Vapour-rise jacket. If I lost it tomorrow, I'd buy another one the same day. One peculiar thing happened that I hadn't noticed before was that my jacket was being covered in what looked like white fur. At first I thought it was small flakes of snow but then I realised it was the moisture coming out of the pores in my jacket and freezing on exposure to the cold air and forming little white hairs... Needless to say I was quite impressed/amazed by this...”

My only problem with the jacket was that it is a bit snug around the boobs. Research of other reviews proved others have experienced the same problem, so make sure you try before you buy.

In short:

It really is as good as they say. You stay comfortable whether exerting energy or resting and it's so, so versatile. Wear it next to the skin for running, add a base layer/fleece for climbing/mountaineering, a hard shell for rain or a down jacket when it's really cold. Or get several Vapour-rises and wear them one over the other!

Price: £110

You can find out more about Sarah at www.sarahstirling.com