BBC News
By Richard Morris
image captionLord West is a former cyber-security minister
The Royal Navy and Britain's merchant fleet, along with most others around the world, rely on satellites for navigation - but what happens if they don't work?
It's a question that troubles the former First Sea Lord, Lord West of Spithead, who has spent months trying to find out if the UK has a back-up plan.
"My concern is that those people who are not friends with us are looking at ways to knock out satellite communications," he says.
"I thought I'd ask the government, I thought they'd have processes, but it became very clear from their answers that they don't understand what the problem is.