Mark co-founded Net-A-Porter with Megan Quinn and Natalie and Arnaud Massenet in 1999. He was integral to the development and implementation of the business model. As Chief Operating Officer he ensured that a great idea was turned into a brilliant business. He instituted a number of groundbreaking initiatives, for example developing a proprietary global taxes and duties engine which enabled Net-A-Porter to be the first truly global fashion website by June 2000.

He remained an investor until Net-A-Porter was acquired by Yoox in 2015.