What's most important - the beginning or the ending of a book?

In my view there’s no question about it – the ending as just as important, and it could be argued even more so. It's the final pages that leave the final impression. When the reader puts the book down that’s what they will walk away with. But here’s the rub: when approaching a publisher or agent it’s always the beginning that a writer is asked for – the first three chapters, the first 3,000 words, whatever. And all the advice is to hone that opening paragraph, again and again and again, to get it as perfect as possible. After all, it’s the beginning that most people look at first, and if it fails to grab their attention the book is returned to the shelf and they move on. Which may be why books with strong openings sometimes seem to trail off at the end, victims of the dictum that those all-important opening pages are key to publication, leading to a sense in the closing pages of anti-climax, of author fatigue. It’s puzzling: why compromise a perfectly pitched beginning with an ending that fails to match. The last two books I’ve read have been masterful – shortlisted for prestigious prizes, or outright winners. But they could have been BETTER – all because of endings that give the impression of mission accomplished, which scamper towards the finishing line leaving the reader with a lingering feeling of being short changed at this most critical juncture of all. I’m sure most authors pay as much attention to the last paragraphs as to the first, but isn't there a danger that the reigning emphasis on the best possible opening can sometimes distract from the need to create the best possible ending as well?

Britten EH blue plaque, Cromwell Road, London