Why did the Vikings invade Britain?

12345
Across
  1. 4. this group of people invade in 43AD
  2. 5. a group of people who arrived from Europe around 6000 years ago
Down
  1. 1. the first people who arrived in Britain
  2. 2. a German tribe beginning with 's' which arrives in the 400s
  3. 3. the area where the Vikings are from