Dorchester on high alert as divisive Swazi king checks in

London's Dorchester hotel is preparing to receive a much noisier crowd than is normal this evening: human rights protesters objecting to Swaziland's king arriving in London.

The five-star hotel, known for its afternoon tea and £450-a-night double rooms, is erecting metal fences around the front courtyard to corral 100 protesters who condemn the decision to invite King Mswati III of Swaziland to Friday's Royal Wedding.

The head of state and his 50-strong entourage are reportedly staying at the Dorchester, according to South Africa's Mail & Guardian newspaper. He is one of 40 foreign royals invited to the nuptials. The Crown Prince of Bahrain withdrew on Sunday following anger about the shooting of democracy protesters in his kingdom, and a wider crackdown which has included the detention of medical staff who treated injured and dying demonstrators.

Tonight's protest is organised by London-based Swaziland vigil groups and will be piggy-backed by Zimbabwean expatriates joining them in solidarity, angered by the decision to invite Zimbabwe's ambassador to take a seat in the front rows at Westminster Abbey.

The demonstrators want to draw attention to the polygamous autocrat's human rights abuses and corruption. Swaziland is crippled by poverty and has the world's highest prevalence of Aids – one in four adults has HIV/Aids.

Extra hotel security will be bought in to control tonight's protests, expected to start at 6pm, according to the general manager at the Dorchester, Roland Fasel. Adjoining streets may be blocked off if large crowds join the protest, and there will be a police presence. Guests at the hotel may have to show room cards to gain entrance.

"If the protest takes place, we will shield off the hotel in a structured approach," Mr Fasel said. "We will protect the periphery of the hotel with Met police and we will bring in additional security.

"We have heard this will be a peaceful political demonstration and we don't want it to take attention away from all the good things happening this week or the fantastic event that is happening on Friday."

Fungayi Mabhunu, a Zimbabwean who is co-ordinating tonight's protest, said: "Swaziland is one of the poorest countries and the king, Mswati III, is the last absolute monarch in Africa who has been abusing people for the past two decades.

"People in the country are dying of starvation and diseases, but they are paying for a man who has 13 wives and an enormous entourage to attend this wedding and stay at this hotel. This is not right."

Yesterday, guests at the Dorchester welcomed the prospect of a gauntlet of demonstrators outside, although some showed confusion about the subject of the protests. One American tourist, who preferred not to be named, said he thought Swaziland was "the name of a drink", while a Jordanian businessman, Mohamed Aldaoud, was initially convinced that the autocrat in question was in fact the leader of Switzerland.

Further protests are expected this week at the Zimbabwean Embassy, against the invitation to Gabriel Machinga, Zimbabwe's Ambassador to Britain.

Despite the Crown Prince of Bahrain's sudden absence for Kate and William's big day – his seat will not be filled – protests against the brutal suppression of political reformists in the kingdom are still expected to go ahead around the wedding festivities, because of the presence of Saudi Arabia's Prince Mohamed bin Nawaf bin Abdulaziz. Saudi Arabia has sponsored the crackdown on democracy protesters in Bahrain.

The Metropolitan Police said 5,000 officers would be on duty on Friday. It said it had rejected an application by Muslims Against Crusades to stage a demonstration outside Westminster Abbey, but that static protests could take place outside the designated zone.

Sixty people who had been arrested at previous demonstrations were banned from entering the City of Westminster and would be arrested if seen in the area on the day, the Met said.