Sky Sports confirmed on Thursday that the medical has been passed in Madrid and now the Welshman will fly into London on Friday.
A deal will then be completed for the 31-year-old to return to the club he left for £85m in 2013, with Real and Tottenham sharing the burden of his £600,000-a-week wages.
Final negotiations are believed to still be ongoing, but all parties are confident that the move will be competed on Friday and he will move to Spurs for at least the rest of this season.
Spurs boss Jose Mourinho would not be drawn on the new arrival on Thursday after his side beat Lokomotiv Plovdiv in the Europa League second qualifying round.
‘Until I’m told Bale is a Tottenham player, I still think and feel and respect the fact he’s a Real Madrid player,’ said Mourinho. ‘I’m not going to comment on a Real Madrid player.’
The left-back impressed on loan for Sevilla last season and was being targeted by a string of clubs, most notably Manchester United in recent weeks.
Bale and Reguilon will join Pierre-Emile Højbjerg and Matt Doherty as Spurs’ summer signings, although they may not be done there, with Mourinho still keen on bringing in a new striker.
Tottenham made an approach for Southampton striker Danny Ings and have expressed an interest in Bas Dost at Eintracht Frankfurt, but have got nowhere with either of those moves.