London Skin is a real phenomenon - every time I travel by tube, horrendous overhead lighting notwithstanding, I’m struck by the generally low standard of the average person’s complexion, and I want to climb up on my seat and start preaching. There seems to be a reluctant acceptance of dull, grey, lacklustre skin sprinkled with clogs, bumps and pigmentation from acne - which is frequently badly concealed by heavy, matte-finish (therefore dull) and clog-promoting make-up. I strongly believe that this is symptomatic of a nation who doesn’t know where to get high quality skincare advice, perhaps a consequence of the fact that there are fewer than 500 dermatologists in the UK (which works out at a roughly one-tenth of the number found in France).

Many, I suspect, wouldn’t even classify their issues as acne - but most will never have known the joy of clear skin’, and the freedom that comes with not having to approach the mirror of a morning as though creeping up on an enemy. This state of affairs makes me want to weep. Great skin is the one beauty ‘accessory’ that looks great on everyone - and unlike a Birkin, is something that everyone can own.

Where to start if you have London Skin?

1) Prune. It’s extremely important that like a good doctor, you do no harm. Get rid of any products that are not non-comedogenic, and I absolutely include make-up (foundations, concealers etc) in this. Be obsessive. Like you have food allergies. Read all the labels and discard, discard, discard.

2) Activate. Skin, which is not perfect, needs things left on it. It is not enough just to cleanse and moisturize-there needs to be filling in the sandwich. The most important thing is a vitamin A-derivative (like retinaldehyde or prescription-only tretinoin). To regulate the way the top layer of the skin matures. If it clogs, then you need this in some form (unless you’re pregnant, in which case there are alternatives). And then you need anti-inflammatories-to kill the nasty red bumps and whiteheads, which are the consequence of the clogs from 6 weeks ago. Benzoyl Peroxide can irritate but at a 2.5% concentration (you don’t need higher) and in a well-formulated product, which may well contain dimethicone, this is now a much friendlier product than you may recall from your teens. Or use BHAs +/azelaic acid in a leave-on format.

Start off applying your actives on alternate days-usually anti-inflammatory in the morning and vitamin A-derivative at night. Treat the whole face, don’t just spot-treat. Otherwise you will never get a handle on it. After 2 weeks, try increasing to daily use morning and night. Stick with it for a minimum of 6 weeks and once its better, don’t stop. Wean down the anti-inflammatories but stay on the vitamin A. Your skin will look better for it in the long run.

3) Rationalise. Cleanser should do just that-and again, should cause no harm. I don’t believe that cleansers alone can fix acne, any more than they can get rid of wrinkles. But they are an essential part of the support system. And don’t over-cleanse with either aggressive foamers, daily physical exfoliants or by double-cleansing. Depleting the skin’s natural barrier will make any ‘actives’ more irritant and you’ll get eczema as well as acne. And then you’ll stop treatment…. and your London Skin will persist and probably look worse.

4) Nourish. Again, the afore-mentioned ‘actives’ need to be given time to work. You don’t acquire problem skin overnight; therefore you can’t expect it to melt away in 72 hours. Give it at least 6 weeks, and probably more like 12…in which time, you will need a moisturiser that allows your treatments to do their thing, and keep you complying. Failing to put your acne treatment on is the single commonest reason it fails. I know this because when I ask my non-responders (who say ‘it didn’t work’) to bring in their treatment bottles, they fidget, avoid eye contact and admit that they gave up after 2 weeks. Usually because they didn’t remember to use this important part of the support system.

After applying your active to clean skin, leave it to penetrate and dry, then moisturize over the top. If you’re very irritable apply a bit before the active (which will lessen its effect, but you can slowly remove this step as tolerance builds).

5) Preserve. Sunscreen, broad-spectrum, SPF50, non-comedogenic, and beyond that, however you like it. But take the time to find one that you are happy to use every day-so important. And one that doesn’t make make-up pill off after it’s applied (a common objection) is out there - you just have to find each other!

6). Enjoy. Remember that once things get better, you must relish your non-London Skin. You will have worked hard, and the rewards should be tangible (if not get thee to a dermatologist). Go to the supermarket without make-up, or something similarly risky, just because you can.

And travel by tube safe in the knowledge that I will be silently admiring your non-London Skin.