This can't be right

In another excellent and challenging article, Mark Steyn comes out with this purported fact:

In 2001, after a Dutch crackdown on benefit fraud, 10,000 Somalis moved from Holland to one East Midlands town - Leicester.

This is an astonishing claim buried away near the bottom of the article. Could one midlands town with a population of about 280,000 really absorb 10,000 Somalis in one year? It beggars belief. Presumably it happened after the 2001 census, though the figures there show the required scale of the subsequent ethnic upheaval.