Mozynski co-founded London Advertising with Alan Jarvie in 2009, having previously run offices for M&C Saatchi in Europe, USA, Asia, Africa and the Middle East.
London Advertising has won the Drum Awards' agency of the year six times in the last seven years. In 2017, they won Agency Grand Prix, International Agency of the year, Best International Digital Strategy, Best Tourism and Leisure Campaign and Best International Campaign.
They are the brains behind the 'Fan' campaign for Mandarin Oriental Hotels, which has seen famous faces such as Morgan Freeman, Stanley Tucci and Rami Malek declare themselves 'fans' of Mandarin.
In 2013 they offered a £100,000 prize for a competition to find the best new digital talent and arranged for David Cameron to launch it at 10 Downing Street.
In June 2020, Breacher appeared on a Leaders Council podcast, discussing the importance of leadership and the role it has played in his career to date.