FYI you really don't need teaching experience to get a good academic job. The number one criteria is excellent publication record.
Going back to the main topic of this post, using too many underpaid academics to teach creates some perverse incentives that are IMHO destroying Oxbridge. Many professors are no longer teaching. Teaching is a great filter. It makes sure they stay up-to-date, they are technically good and they take pride in their research field. Professors that are really good and passionate, i.e. Terry Tao-like personalities, are often getting displaced by ladder climbers. This is especially common in experimental fields and really disheartening.
Not least because in academia, either you teach, or you do research. You can't do both.
>> Teaching is a great filter. It makes sure they stay up-to-date, they are technically good and they take pride in their research field.
If that's your experience, that must be something that depends on the field of research and we must be in different fields. In CS, teaching is indeed a good filter- in the sense that it separates the teachers from the researchers. I have the direct experience of my PI, who has not done a day of research after becoming a lecturer. Because there is no time. Teaching takes so much admin work that there's no time left for research. I mean any above-junior academic position takes too much admin work, but teaching really gets the cookie. My experience so far has been that senior academics who still take an active role in research find ways to avoid teaching like the plague. Although you can't really escape it. You'll at least mark some papers in your subject, whether you like it or not (and with TA-ing from PhDs or not).
A high-end fellowship like the ones you mention is also fine if you want to improve your publication track record. In some fields getting a lectureship after your PhD or postdoc might be extremely difficult as the market is too crowded.
Yes, unfortunately. I'm not saying it's easy, but from what I can tell it's possible: you can have your entire academic career as a long string of fellowships.
>> Lectureships demand significant research and teaching and supervision experience.
Yes, but we know that in practice what that means is that the professor leaves the research work to their PhDs and post-docs, and then puts their name on it at the end. Sometimes that's because the professor has run out of good ideas, sometimes it's because they don't really care, most of the time it's because their lectureship duties leave them without enough time to do it.
This was not my experience during my PhD, btw, my supervisor (who is retiring next month, three years after supervising my PhD) was an active participant in my research and he had his own totally hands-on line of research that he pursued separately ... and whenever I told people about that they were full of surprise. "Don't tell me that he is still coding?". That sort of thing. People were surprised because that just doesn't happen.
>> In some fields getting a lectureship after your PhD or postdoc might be extremely difficult as the market is too crowded.
I've had an offer that I turned down because it was in China, and a discussion about another in the UK that I didn't even consider. Teaching is the death of a research career, that's what I've seen and I'm not going anywhere near it. What that means I don't know. It's possible that my research career is already over anyway- next week is the last of my post-doc and I don't have anything lined up after it :/
It depends on where you are. British universities value teaching more than American ones, which are more focussed on research.
This is not true in general. In NZ, most academic positions are 40% research, 40% teaching, and 20% admin. Lecturers, distinguished professors, and everyone in between. Big research grants can provide temporary buy-out of some teaching, but it's explicitly part of the role, and not often reduced completely for long. Maybe 10% of academic roles at my university don't include research.
A 40% teaching is the most research-intensive contract you can get at most universities.
Good departments will still let you enjoy a sane workload because they will allocate a realistic amount of that 40% for teaching preparation, marking duties, etc.
I mean that's why most mid-level and senior academics leave the research to their PhD students and post-docs. Yes? Because they don't have the time to do it themselves.
... although my PI didn't :)