Foreign species invading the UK

As international trade increases, particularly by sea, we're seeing more stowaways; but not of the human variety. Scientists are reporting that animals and plants are hitching rides around the world on boats - and even on fishing tackle. They then setup home in other countries where, with nothing to eat them, they can become dangerously invasive. Timothy Revell spoke to David Aldridge an expert in invasive species about the UK's most recent arrival.