Sumner Redstone has bought almost two years’ breathing space on the $1.6bn debt load threatening his grip on Viacom and CBS, but has had to offer his stakes in both media empires as security for the first time, making them vulnerable should he be unable to make repayments.

The 85-year old mogul disclosed few details but is understood to have agreed to much higher interest rates in the new agreement with banks, which was reached last week but announced on Friday evening.