What's good for removing tar?

I went out in the wet yesterday so was expecting to come home a bit muddy from the lanes....but when I went to clean my bike, I realised that there was a lot of tar on it. The bike has mostly cleaned up OK (a few sticky smears left). The worst bit is my white saddle, which is now a browny shade of white. 
What is the best thing to remove tar?
Also, probably a daft question, but seeing as I didn't ride on any newly surfaced roads, where could it have come from? Is old, displaced/broken up surfacing sticky too?

What is the best thing to remove tar?
Also, probably a daft question, but seeing as I didn't ride on any newly surfaced roads, where could it have come from? Is old, displaced/broken up surfacing sticky too?
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In terms of where it came from, newly filled potholes perhaps? Quite impressed you could get tar on the saddle. Or did you sit on the road?
Thanks for the tip. Will try a bit of white spirit on it.
You can buy it in Halfords.
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Or butter - it's what my mum always said. Might make the saddle slippery or leave grease stains instead though!
that's because it leaves an oil residue on the braking surface - which is not ideal.
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Cervelo
Campagnolo
+1 for removing from skin. But it'd probably stain a saddle.
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I used turps as I couldn't find any white spirit and it seems to have done the trick. (I probably should have done it outside and not in the kitchen (complaints about the smell) and I think I've made a big mistake in doing it 20 mins before I get on it rather than waiting until I next washed it. . :oops: . )