When Kate fell out of favour with the fashion set in 2005 following allegations of drug taking, it was Mario who spoke up in her defence.
"I know Kate very well and I don't think she's at all tormented… "I have to say I'm not a witness to seeing her debauched or out of control," he said at the time, going on to praise her professionalism.
"Since 15 until today, she's never not been there on a shoot, never said to me, 'I'm tired, I don't want to work' - never. She works from eight in the morning 'til 12 at night if need be."
The close friends were both in Umbria, central Italy for the nuptials of former Storm model agency booker Jess Hallett, who was marrying her Italian beau Pietro Birindelli.
Pretty in a short red summer dress and black ballet pumps, Kate was there in her capacity as matron of honour. And the model, whose new Topshop collection went on sale last week, brought along her six-year-old daughter Lila Grace.
Last month the supermodel organised the hen party for her friend. Thirty-five-year-old Kate hired a barge to take the group along the River Thames to Oxford, stopping at several pubs along the way.
The celebrations ended with a big party at the British beauty's converted home in Oxford.