What is Schedule 7 of the UK Terrorism Act?

The Guardian newspaper has criticised Schedule 7 of the Terrorism Act, which police used to detain David Miranda at Heathrow airport for nine hours.

• Schedule 7 applies only at airports, ports and border areas, allowing officers to stop, search, question and detain individuals
• Guardian editor Alan Rusbridger called it "a vacuum" with no checks and balances
• Detainees must provide "any information in his possession the examining officer requests"

• Police can hold individuals for up to nine hours
• The Home Office says more than 97 per cent of examinations last less than an hour
• Police say property not returned straight away can be kept for up to seven days, or longer if it is required "for use as part of a criminal investigation"

• The Home Office states Schedule 7 should be used solely for the purpose of ascertaining if a person is involved in "acts of terrorism"
• David Anderson, the government's independent reviewer of terrorism legislation, has called its use to detain Miranda "unusual".

David Miranda's solicitors have said they are challenging the "legality of the action" to detain him under Schedule 7.