The gross spend was 90 per cent higher than the previous record of £430m in 2018 and almost triple the previous January window (£295m).
Southampton added plenty of firepower on deadline day with winger Kamaldeen Sulemana and 201cm striker Paul Onuachu for a combined £40m.
Sean Longstaff’s double on Tyneside secured a 3-1 aggregate victory over Southampton and a trip to Wembley.
All parties were on board with Hakim Ziyech's loan from Chelsea to Paris Saint-Germain, but a paperwork error reportedly prevented the deal.