Michael Phelps started swimming when he was seven, partly to release some of the energy he had after being diagnosed with ADHD. He was obviously a fast and competent swimmer - but that's not the end of the story.
If he'd never learnt to do racing turns, control his breathing, improve his stroke - he wouldn't have won one medal - let alone 22 Olympic ones.
And what does this have to do with writing? For some reason writers are assumed to drop, fully-formed, into a sea of creativity and just swim. They either have talent and float, or none and sink.
Nothing could be further than the truth. Writing is a craft, and you can take lessons and learn tips to get your craft smoother. There isn't anyone whose writing can't be improved.
What you can't teach is 'voice' - the unique flavour of someone's writing - their authorly fingerprint - but sometimes that voice is drowned out by a myriad of small errors, and the writer needs help.
There is an ongoing debate as to whether editorial services are benefitting authors or exploiting them (see this opinion piece in The Bookseller - and my reply on my own blog here) and I come firmly down on the side of benefit.
If you've employed someone to help with your writing - have you found it helpful? How long have you been writing for - has your writing improved in that time?

Christina Howland on August 24, 2012
Hi Cressida,
1An interesting blog. I have been for a few years now studying with the Writer's Bureau in order to improve my writing and I believe it has improved in the time that I have been doing it.
I have also found that doing the course I am on has also broadened my horizons and there are other areas of writing, after thinking I didn't like them, have enjoyed doing. It has also shifted my persepective on my work and writing as a whole and don't feel just as niave as I was in the beginning.
Adrian Sroka on August 24, 2012
Hi Cressida.
I read the Bookseller piece, your blog on The Book Analyst, and the replies.
I believe there are genuine editors and editorial services out there, but there are many bad apples as well.
Budding authors should not assume that editors who have gained university degrees in literature are dedicated to their jobs. However, I can tell, that you, and other guest bloggers are, dedicated professional people, who mine through slush piles in search of gold.
Doctors are highly qualified, but not all doctors are good. The same can be said for other professions where one expects a high standard of service.
When budding authors have been misled, I believe it is because budding authors did not research the best editors, or available editorial services out there. Recommendation is a good guide before choosing an editorial service. I believe the services offered on this site are good, having heard reports from those that have attended them.
There are good creative writing courses, but I question the value of many non university creative writing courses. In particular ones with large classes. I fail to see how a student can gain the maximum benfit for his/her money when a teacher has many students. He or she, cannot possibly give their undivided attention to an individual.
In answer to your question, as to whether editorial services are benefitting authors or exploiting them. There are good examples of both, but the boom in self-publishing has created a rapidly growing market where many want-to-be authors have been badly exploited.
Unfortunately, this trend will continue until budding authors are aware of the best available editorial services.
Victoria Whithear on August 25, 2012
I don't agree with everything Peter Cox says as he does seem to try to discredit editorial services in general. As you say, you offer a service which supplies the reasons for rejection from an industry which doesn't have the time to supply them. It is a valuable and valued service. For those not seeking external comment from amateurs, possibly even a completely necessary one. Even glaring errors can be missed if you've stared at a text too long and it's easy to ruin your reputation with an agent before you've gained one.
1But I'm afraid he's right to say there are people prospecting the hopes and dreams of wannabe writers. There are a lot of writers making it very easy, though. While there are people treating novel-writing like a gold rush, there will be people selling 'tools' at outrageous prices to the uninitiated.
I've been on courses. One of my tutors kept in touch and still gives encouragement via Facebook which is a real boost. I still hope to be able to attend workshops or courses at Bloomsbury in the future, work, kids and life in general permitting and the next step for me is to decide whether to get an appraisal or try submitting without. I think if you spend time selecting the correct services for your needs and don't go chasing promises made by those who can't deliver something your must produce yourself, you can't go far wrong.