Apologies fifths has already been mentioned:

"Top Ecuadorian Diplomat Destroys Guardian's Claim That Manafort Visited Assange"

…"Narváez - initially consul and then first secretary at the embassy, told the Canary that to his knowledge, Manafort never visited the embassy while he was employed there. What's more, his account supports points made by The Intercept's Glenn Greenwald about visitation rights at the embassy."

"It is impossible for any visitor to enter the embassy without going through very strict protocols and leaving a clear record: obtaining written approval from the ambassador, registering with security personnel, and leaving a copy of ID. The embassy is the most surveilled on Earth; not only are there cameras positioned on neighbouring buildings recording every visitor, but inside the building every movement is recorded with CCTV cameras, 24/7. In fact, security personnel have always spied on Julian and his visitors. It is simply not possible that Manafort visited the embassy."

https://www.zerohedge.com/news/2018-12-03/top-ecuadorian-diplomat-london-embassy-destroys-guardians-claim-paul-manafort