Industry sources said the Saudis could be spending close to £1m on the campaign, which includes dozens of prime poster sites around London and newspaper ads.
"He is bringing change to Saudi Arabia," the ads say, with a large photo of Crown Prince Mohammed bin Salman and the hashtag #ANewSaudiArabia.
The ad takeover includes some many premium outdoor locations, including the Cromwell Road "domination" site, four screens in a row on the main A4 road from Heathrow to central London.
One source has estimated the ads could be appearing on as many as 50 digital outdoor poster sites around the capital.
The ads began appearing on Monday, ahead of the Crown Prince's meetings in London with Theresa May and the Queen, which are due to begin on Wednesday.
The 32-year-old prince is on a diplomatic mission to show that Saudi Arabia's conservative rulers are willing to modernise.
He has already showed his ambition after he ordered an anti-corruption crackdown last November when scores of leading Saudi business figures were detained and their assets seized.