Most UK universities place a lot of value on teaching experience. If you have a PhD degree from Cambridge or Oxford, a decent publication track record and significant teaching experience, you will typically get lectureship (assistant professor) offers straight after you finish your doctoral studies. Some teaching experience will be valued more than having a stellar publication record, especially if you have a good research plan. It makes sense because most lectureships involve at least 40% of teaching and supervision.
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.
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.