According to local press, the demonstrator – who is still refusing to come down – is believed to be Adam Jammeh, a former employee of Tesco and Total Security Services (TSS) who was fired after being accused of stealing from the store.
The man, who has been balancing on the girders of the building for the past 17 hours, has been live-streaming the sit-in on Facebook.
In his latest video, he claimed that he had been denied water for “hours and hours and hours”.
“Since yesterday evening I have asked for water,” he said. “The police are still here – they are in reception with the paramedics. They are still denying me water, people.”
Emergency services, including police, fire officers and paramedics, all rushed to the shop after the incident began.
In another video, the protestor apologised to customers, telling them: “Sorry for some of you that are supposed to come here shopping in this store. It’s inconvenient, sorry for that people but it’s something I have to do.
He added: “I’ve been protesting for the past six months and they [Tesco] know about it.
“Today, the Tesco CEOs need to come up here, and explain to me why I lost my job.”
His wife, who is outside of the store supporting him, told the BBC “he will not be coming down willingly” and they are prepared to “accept the consequences”.
A spokesperson for Tesco said: “We’re aware of an incident at our Reading West Extra store and are assisting police with the matter.”
Royal Berkshire Fire and Rescue Service said they had received two calls about the incident.
Tesco Extra Reading West has been closed for the past 14 hours due to one man protest being staged in the roof pic.twitter.com/csv1EaF8iA
— Nick Johnson (@nehjohnson) October 13, 2017
A spokesperson said: “At 6.38pm on Thursday, 12 September and 10.15am on Friday, 13 October, Thames Valley Fire Control Service were called to assist Thames Valley Police with a rescue from height at a commercial building on Portman Road, Reading.
“On the first call, a Royal Berkshire Fire and Rescue Service crew from Caversham Road Fire Station was sent to the scene and on the second call Dee Road Fire Station was sent to the scene.
“Crews have returned to the respective fire stations and will provide further assistance to Thames Valley Police if required.”
TSS and Thames Valley Police have yet to respond to HuffPost UK’s requests for comment.
Video: Tesco CEO Dave Lewis says the group is “more competitive” (ITN News)