The Brazilian-born designer, whose label, Issa London, is based in the UK, has dressed everyone from Naomi Campbell and Madonna, to Princesses Beatrice and Eugenie.

But it is Kate Middleton, who wore an Issa dress yesterday  to announce her engagement to Prince William, who is perhaps Helayel's most famous client to date.

How Kate's favourite designer became a fashion must-have - Fashion - Daniella Issa Helay - Issa London - Kate Middleton - Prince William How Kate's favourite designer became a fashion must-have - Fashion - Daniella Issa Helay - Issa London - Kate Middleton - Prince William

Sexy yet demure: Kate Middleton wore an Issa dress to announce her engagement to Prince William yesterday

The deep blue hue perfectly matched the sapphire stone of her ring, while the wrap detail made the most of her slender waist. At once sexy and demure, it was a perfectly judged choice for the bride-to-be.