The lecture was about his three year research project into how to maximise flavour in home grown produce. He's a great speaker, it could have been very dry as there were a lot of figures and statistics, but he was very funny with little asides and he spoke very fluently, no 'umm's or hesitations so he was easy to listen to.
The research is summarised in his book, Grow for Flavour. He found that the biggest impact on flavour was genetics, if you buy the right variety (rather than the one with the biggest picture in the catalogue) then you're most of the way there.
There were also loads of useful tips, like smaller berried varieties generally have better flavour than large berried varieties, especially true of blueberries and strawberries. Aspirin is a stress hormone for plants, so if you spray the leaves of young plants with half an aspirin per litre of water it will think it's under attack and grow more vigorously. While your plants are still seedlings, rough them up a bit by running your hand over them, they will think they are in a windy environment and grow stockier and bushier. He had an amazing technique for tomatoes too, which is a bit long to describe but might be on his website or Facebook page.
I am almost inspired to clear the weeds out of my raised veg beds and actually plant something next year.