I get asked this question frequently by people who are considering a career change. Here is my story.
The first 10 formative years of my career were spent with McKinsey, a strategy consulting firm, working in the London and Amsterdam offices with projects pretty much in every country in Europe. My stay there was a bit different than the norm: 1) I stuck around for about 10 years, versus 2-3 on average, and 2) I did not specialise in one industry (banking, consumer goods, etc.), but rather did a functional specialisation: mergers and acquisitions, usually on the sell side. In short, I helped big Fortune 500 companies sell themselves to other big Fortune 500 companies. As a result, every project that I worked on was in a different industry, and I had to adjust rapidly to understand a completely new field of work (beer, pet food, DIY retailing, petrol retailing, grocery, retail banking, asset management, insurance, private equity, e-commerce, mobile payments, postal services and logistics just to name a few). Little did I know then, how useful this skill would come in a decade later in a briefing for a new presentation design project.
After leaving the Firm, I moved with my family to Tel Aviv where I started out as an independent strategy consultant. Soon, I got in touch with the Israeli high tech industry. The small startups could not afford (and probably did not need) me as a strategy consultant for 6 months but saw value in my PowerPoint slides for meetings with potential investors (these charts were still B&W, highly organised, full of consulting speak at that time). It was here that my gradual transformation to a presentation designer started. Gradual is important here, I think no freelancer figures out exactly his professional niche from day one. In my case it probably took around 2-3 years to stop calling myself a strategy consultant.