Natalie Portman from brunette to blonde

Natalie Portman's hair transformation is a fabulous example of how to go from dark to blonde in style. Organic colour specialist Karine Jackson, christened 'the queen of blonde' by a host of journalists for her faultless colour transformations, gives her tips:

Going from dark to blonde is always going to be difficult on your hair. To achieve the best blonde the first thing you need to do is determine your natural shade. You can then go 3-4 levels lighter. This is what Natalie has done and the colour works beautifully. If you can test the colour prior to the service I would recommend doing so!

It might be easier to lighten up in stages, so start with some highlights. This also gives you a chance to get used to being lighter.

Use a gentle colour that contains organic ingredients where possible and contains no ammonia. I recommend Organic Colour Systems - it uses heat to open the hair's cuticles to absorb the colour instead of ammonia so is much less drying.

Generally speaking, going lighter is more damaging than going darker, so you need to give your hair lots of replenishing treatments. Hair either lacks moisture, protein, or a mixture of both. To test the condition of your hair, you can do the "stretch test". Take about 10 strands of hair and spray with water, hold the hair firmly between both hands and gently pull the hair away from the head, healthy hair should stretch about 30% of its length and then return like an elastic band showing no signs of damage. Hair that stretches and returns is healthy, hair that stretches and does not return to its previous length is weak in protein, hair that doesn't stretch is low in moisture.

Make sure a full blonde change is practical to upkeep. If you have an all over blonde, your roots will need doing every 4 weeks or so - have you got the time and money to do this? If not, go for highlights that are more broken up at the scalp - regrowth is disguised for longer. You can see from Natalie's style that it also looks beautifully natural when it's broken up with shades closer to her natural colour, especially near the roots - this is a much better look for regrowth.

Blonde hair needs to be cared for properly or it'll go brassy. Wash once a week with a special blondes shampoo, such as Organic Care Systems Silver Shampoo. Look out for shampoos that are tinged blue or purple - these are best for counteracting any yellowing.