In Defence of Flashback

I know that some writers – and editors – view the use of flashback with some misgivings, objecting to it because the reader is made to look back at events which have already happened and therefore knows there is a positive outcome (your heroine is still alive and compos mentis) meaning that the narrative tension is diminished.
I'm currently plotting a novel and I'm definitely going to tell some of it in flashback, for a number of different reasons.

• Looking back at something which has happened enables the writer to put a spin on events. They don't just happen sequentially, they can be viewed through the lens of the present, which gives you the potential to examine them more obliquely and add layers of subtlety. It's rather like lighting a scene for effect – do you use soft, rosie tones or go for a cool, blue hue? What you might possibly lose in tension, you certainly make up for in atmosphere.
• I don't believe that suspense is necessarily diminished. The reader knows that the protagonist has got from point A in the story to point B, but they have no idea of the route taken, the pitfalls, or the high points. In a novel written sequentially you don't know whether the heroine will make it to point B, but generally speaking they do, so it seems to me that nothing is lost.
• Writing in flashback can allow you to use an unreliable narrator, which is another way of adding tension to your work, as the reader gradually comes to see that the account given by your central character may not necessarily be accurate and unbiased.
• Using flashback enables you to exploit the full potential of dramatic irony, where the reader knows more than the characters do, thus giving a different kind of tension to the story.

It also has to be said that a number of writers have used flashback to dazzling effect. Off the top of my head, I'm thinking that Wuthering Heights opens with the ghost of Cathy outside the window and Heathcliff in terrible distress calling out to her. Emily Brontë then goes on to describe the course of their ill-starred relationship, but knowing from the outset that it ended tragically means the narrative is shot through, not just with dramatic irony, but a delicious kind of poignancy as well.
And one of the most famous opening lines in modern fiction is Last night I dreamt  I went to Manderley again...I don't suppose anybody had the effrontery to tell Daphne du Maurier to avoid writing in flashback.