Victoria Beckham style dresses - where?

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I saw someone wearing a Victoria Beckham style dress today and it looked fab! I'm assuming it wasn't the real thing, so I wondered where I might be able to get one?

It had sleeves to the elbow, wasn't low and may have had an asymmetric neckline, slightly below the knee in length.

I'm open to suggestions with colour but would love blue!

Help!