"The new technologies result in new work that hadn't previously been envisaged. How many of the people reading this have a job that even existed 100 years ago?"
In the 19th Century (~100 years ago) there were over 3 million horses in the UK and they were mainly working animals. Today there are about a million, mainly in leisure and sports. We haven't been able to redeploy all the horses because they're not up to doing the jobs we have. That's the danger of robots and AI -- that not everybody is up to doing the jobs for which, yes, there might be a huge demand.