In a video message to the team from Downing Street, the PM said: “I want to wish Rangers the very best of luck in tonight’s Europa League final.
“A lot has happened to the club since you last had a game like this to look forward to, so it is a fantastic reward for the fans’ dedication, through thick and thin.
“And it’s always great for sport, and for the UK as a whole, to see our great teams performing on the grandest of stages.”
Mr Johnson added: “So, whatever happens on the pitch, I couldn’t be a happier to see you flying the flag out in Spain, and I know that you will do us all proud.
“Good luck.”
Almost all of the 100,000 fanatical travelling supporters of the Glasgow giants have now arrived in the Andalucian capital and they were partying like it was 1972 into the early hours of match day.
Rangers only previous European success came in the 1972 when they defeated Dynamo Moscow at Barcelona’s Camp Nou to lift the Cup Winners Cup.
Rangers legend Ally McCoist has been enjoying the party atmosphere in Seville, and has promised to turn the celebrations up another notch if his beloved Gers can do the previously unthinkable and lift the silverware.
Speaking to Gabby Logan on TalkSPORT, he said: “Gabby, I am going to throw my wallet to the crowd if we win tonight.
“I am going to throw credit cards about, it will be deep joy.
“Gabby, I can’t tell you how buzzing I am. We had a marvellous night last night”.