what to do when an ebay seller doesn't respond

i bought the sullivans volume 2 on dvd from ebay, i paid £40 for it and it arrived this morning by royal mail and the dvd case was broken and cracked open? i feel upset by this as it was the last one in stock and i was a big fan of the sullivans tv show way back.....anyhow i messaged the seller this morning explaining the situation, that it arrived cracked and smashed in by roya\l mail...but the seller isn't responding, and it's evening now. what can i do?