What to do for entrance into Cambridge/Oxford?

It seems that you're currently doing your A-levels so I assume you're already doing at least maths and physics. You need to do well in your A-levels - predicted at least A*AA.

For Cambridge, they place a lot of emphasis on your UMS scores at AS-level when you apply so you should preferably have 95+% UMS. You would then probably sit a test (either the TSA [thinking skills assessment] or a test within the college were you to be called for interview, depending on college) and then potentially get an interview.

For Oxford all applicants must sit the PAT [physics aptitude test] which you should do well on. Oxford also consider GCSEs more than Cambridge. Using this information you may get called to interview.

The interviews would consist of solving some form of problem with a maths/physics basis.

Your academic record + potential is the most important thing for Oxford and Cambridge - they hardly care at all about any extra-curriculars etc.

I am unsure about Imperial but I would not be surprised if they similarly are looking for mathematically brilliant candidates considering that they're of a similar standard to Oxbridge.

Well I Study in Oxford and in Harvard for 5 years in both. I was taking medical (neurosurgery). If you are looking forward of becoming and engineer and you want to make your career at Cambridge or oxford than try to take the most advanced physic and math classes (calculus). entering oxford engineering course means that your GPA needs to be higher than 3.8+. and your average in physic needs to be 88-92% and in math 84-89%. If you still haven't completed your 40hrs community service than go engineering websites and apply. if your done yours hrs. then do another 40 hrs just on engineering. You can apply for Oxford's engineering if you meet all these requirement.

The site I have posted below is a engineering volunteering site.

Sorry for your inconvenience I don't have any actual website source. I know all this because I was a oxford professor in Medical before I started working as a Neurosurgeon. and trust me once you get into Oxford and complete your engineering course and when you graduate and look for a job you will receive job offers paying you 180k at starting (benefit of going to good universities)

its a good thing you want to become an engineer and not or surgeon because I stayed in university for 11 years! I was 30 when I graduated. but my salary is great success since I m a gold medalist neurosurgeon who graduated from Harvard and had clinical rotation at Oxford my current salary (wage) is $3 million