We were told to write 2 drafts over the summer holidays, writing each from scratch and then combine the best bits of both to create the final thing. I guess I spent 5 hours in total.
For us the suggestion was not to try and write the first paragraph as it is the hardest to write but just write some of the others and see if any of them seem like a first paragraph and then switch the paragraphs around accordingly seemed to work, I got in everywhere I applied including Oxford.
The more things you have done the easier it is to write.