The Tower of London will build its own breeding aviary in a bid to avert "a raven crisis".
King Charles II's decree states that at least six ravens should be kept at the tower at all times or "the kingdom will fall".
There are currently seven ravens at the tower - Jubilee, Harris, Gripp, Rocky, Erin, Poppy and Merlina.
But with only one raven in reserve, the breeding programme will ensure "the prophecy will never come to pass".
Historic Royal Palaces has been given planning permission by Tower Hamlets Council for the aviary, according to the Local Democracy Reporting Service.
The construction will be 12m long, 5m wide and 3.5m high and located in the moat, next to the famous Salt Tower. It is likely to be built next year.
In a report submitted to the council, Historic Royal Palaces warned it was becoming "increasingly difficult" to source the birds because "there are very few legal captive raven breeders in the UK".
The breeding programme will be overseen by the Ravenmaster, Chris Skaife, who feeds his charges 170g of raw meat a day - including mice, chicks, rats and, as a treat, blood-soaked biscuits.
Ravens were once common in Britain but are now protected with 7,400 breeding pairs left.
Breeding pairs must have their own territory, and so cannot share the Tower's current enclosure.
During the Second World War, the ravens at the Tower were used as spotters for bombs and planes during the Blitz.
When numbers fell to just a single raven guard, Winston Churchill ordered that the flock be increased to at least six.
An RSPCA spokeswoman said: "We're hopeful that the ravens will be cared for at the highest standard and that the British Crown and the country are safe for the foreseeable future."
- The birds were protected in the 16th Century because of an ability to scavenge and dispose of carrion
- By the 19th Century they were classed as vermin
- Six are kept at the Tower of London by a royal decree issued by Charles II. Legend has it that if the birds leave the site, its White Tower will crumble and the Kingdom of England will fall