Queen Elizabeth's death certificate released - here's the cause of death

Britain's Queen Elizabeth II died of old age, according to her death certificate released Thursday. 

Britain's longest reigning monarch died hours after the palace revealed she was being placed under 'medical supervision' while staying at Balmoral, where the royal family rushed to be by her side. 
The queen's death wasn't announced until 6.30 p.m. (1.30 p.m. ET), a seismic moment in British history that halted news broadcasts and launched 10 days of official national mou ing. 
A grand procession of events to mark her death was followed around the world, culminating in the solemn pageantry of her state funeral in London and subsequent private burial at Windsor. 
The certificate was released on Thursday by the National Records of Scotland, which confirmed that her death was registered by the registrar general for Scotland, Paul Lowe, in Aberdeenshire on Sept. 16. 
The certificate was signed by Princess Anne, the queen's only daughter, who accompanied the monarch's body as it made its way from Scotland to London for its five days of lying in state. 
Thousands of mou ers from across the world joined a line stretching more than 5 miles along London's River Thames to pay their respects and see the queen's coffin in Westminster Hall.
The queen