American rapper Pharrell Williams was forced to apologise to an Irish TV presenter after refusing to answer questions about troubled singer Britney Spears. Williams, 34, was asked by Xpose presenter Karen Koster if he would consider another collaboration with Spears - six years after the release of their hit I'm a Slave 4 U. But the hip-hop star reacted furiously to the question and stormed from the stage. However, he later apologised for his actions. Koster says, "He was pretty annoyed when I asked the Britney question but then he softened a bit. Later I thought we were all done, but he comes over, places his hand on my back and says that he still felt bad."