Teaser 2565: Red and black

From The Sunday Times, 20th November 2011 [link]

I have taken 10 cards and written a different digit on each one. Some of the cards are red and the rest are black. I have placed some of the red cards in a row to form a long number. Then I have moved the last card to the front to give me a larger number. In fact this larger number divided by the original one equals a digit on one of the black cards.

What was the original number?