I left Amazon and became an angel investor. Mentoring startups for 6 years made me a better founder.

• William Tunstall-Pedoe co-created the technology that would become Amazon Alexa.
• After leaving Amazon in 2016, he mentored startup founders and became an angel investor.
• Tunstall-Pedoe said these experiences prepared him to become a founder for a second time.

This as-told-to essay is based on a conversation with William Tunstall-Pedoe, 56, an angel investor and founder based in the UK. This piece has been edited for length and clarity.

In 2012, I sold my first startup, Evi, to Amazon. It later became Alexa.

That gave me the capital to invest in the next generation of startups when I left Amazon in 2016. I leaned into that opportunity, becoming both a mentor and a very active angel investor.

It was one of the best experiences I've had for career development, because I saw almost every situation that a startup can encounter, both good and bad.

I started saying yes to things

When I left Amazon, I suddenly found myself with an empty calendar.

I wanted to take a break — six months or so — but I still needed to do something with my days. My calendar filled up faster than I expected.

I started saying yes to things I would have turned down while working at Amazon. I was invited to a party in San Francisco, which is a long way to go when you live in the UK, but I went anyway. I booked a hotel for a couple of weeks and let my time fill up with meetings and other activities.

The year I left Amazon, 2016, turned out to be a really extraordinary time for me, when I traveled a lot and did some very interesting things.

I gained experience as a mentor and angel investor

One of those was being invited to help the Creative Destruction Lab, a seed-stage program for scalable science and technology-based ventures, founded in 2012 by economists at the University of Toronto's Rotman School of Management.

The premise was simple: mentors who successfully launched companies, like me, provided startups with expertise. Every few months, the mentors and startups would meet to set clear objectives for the next stage of development.

It was a bit like the "Weakest Link." We'd cut companies, sometimes if they'd fallen short of their goals, at each meeting. Over the course of about nine months, the cohort would narrow, and mentor time and resources would be focused on fewer and fewer businesses.

I did this for about six years. I would fly back and forward from London to Toronto every few months, making angel investments in dozens of promising companies, and for another two years when the program moved to the University of Oxford in 2019.

Around the same time, I became involved with Cambridge Angels, an invite-only network of experienced investors, which gave me exposure to a wide range of early-stage companies and investors.

I knew I wanted to be a founder again one day, but waiting turned out to be the right decision. My time as a mentor and angel investor was great preparation.

By mentoring hundreds of founders and investing in many, I added to my 10-year deep experience in one startup, Evi, with the much shallower but broader experience. It was also super interesting to have this vantage point over so many other startups.

Founding my second startup was very different to my first, Evi

When I founded my second startup, UnlikelyAI, in 2019, the experience was very different from the first time. I still made mistakes and ran into problems, but I was no longer a novice founder with no support.

This time, I had the capital to fund the business myself for a while. When I later raised a friends-and-family round, it was largely made up of prominent angel investors I'd met through mentoring and angel investing.

As a second-time founder, not only did I have a decade of experience from my first startup, but I also had something to complement it: the invaluable, vicarious experience of mentoring hundreds of other startups.