As reports of desperation mounts, governments of France, Britain and the Netherlands, who administer a number of territories in the region, have had to defend themselves against criticism over their response to the disaster. He will meet Governors of the affected Territories and others who are leading the recovery work, and visit communities working to fix the extensive damage they have suffered.
The UK government has pledged £32 million to cover the immediate emergency response needs.
"The U.K.is going to be with you for the long term", Johnson had told residents in a video message.
Some residents criticised the United Kingdom government's emergency relief response as "pathetic and slow", reports the website.
"The French and American governments clearly get the scale of the crisis in a way that the British government seems slow to grasp", said U.K. Liberal Democrat leader Vince Cable.
"Basically, life-saving commodities is what we are getting in there", he said.
Anguilla suffered extensive damage, and at least one person there has been confirmed dead.
He toured Sint Maarten, the Dutch section of the island, on Monday, before meeting residents on Saba island Tuesday.
Mr Johnson called it the "biggest operation our armed forces have conducted since Libya".
Branson, along with about a dozen Virgin Group staff members, had a sleepover of epic proportions on Necker Island which has withstood 3 hurricanes in the past 30 years.
As Royal Marines and Royal Engineers arrived at the hospital to help with repairs, Mr Johnson said to them: "They need you badly in there". "Everyone's helping everyone. We're all trying to stay positive".
There are a lot of ways to measure the strength of Hurricane Irma, including its viciously fast wind speeds, the multiple people it killed and the millions more left without power or with damaged houses.
"The military presence is really ratcheting up now", he said.
More than 1,000 troops have been sent, with looting a key priority.