Q. After cleansing and toning, I use a serum but I don't always like to add moisturiser before I apply my foundation.  Is that OK?  I do want my foundation to last. A. The general rule is this:  a serum is not a moisturiser.  A serum is a way of getting lots of lovely nutrients into the skin in a few drops of light formulation.  So, generally speaking, you need a moisturiser too, for hydration and healthy cellular function.  (Cells communicate best when they're adequately moisturised.)

However, it does depend on your skin type and what happens with your foundation (which you don't specify).  If it disappears during the day and you have to add more and more base, the likelihood is that the skin surface is not optimal.  In which case, we suggest a light slick of serum followed by a moisturiser.  (Which is what we do ourselves.)

It may be that you are using lots of serum (which is probably costing you a small fortune), then a super-hydrating foundation on normal to oily skin - which might work fine for you.  If it does, of course you don't have to change:  we're of the 'if it ain't broke, no need to fix it' school of beauty advice.

But the key for us – and the experts we know – is nevertheless to apply a serum, followed by a moisturiser in the mornings.

The best tip we know for lasting foundation, meanwhile, is to leave the moisturiser to sink in for a few minutes before applying your base.

If you are going out in the evening, you might even want to consider a primer, which will give a lovely smooth surface and keep your foundation in place for ages.  As a finishing touch, a dusting of translucent powder or a finishing product like the award-winning Bobbi Brown Brightening Finishing Powder - one of our favourites - will keep your complexion radiant while you dance all night!

•  Bobbi Brown Brightening Finishing Powder in Brightening Nudes/£40 at www.johnlewis.com.com - buy here