Foreign dignitaries must share buses to travel to the Queen’s funeral | Queen Elizabeth II

Foreign heads of state arriving for the Queen’s funeral must travel by bus en masse to Westminster Abbey, rather than using private cars, according to newly issued government guidance.

The documents, seen by the Guardian, set out strict rules for the dozens of international presidents, kings, queens and prime ministers expected to attend the funeral, urging them to travel by commercial flights to avoid swamping London’s airports.

The instructions lay bare the logistical challenge of accommodating the sheer number of overseas dignitaries who will be arriving in London over next weekend – and will pose a dilemma for Joe Biden, who is likely to require a significant amount of additional security. The US president has confirmed he will attend the funeral in person.

The guidance, first reported by Politico, says that international guests must keep their delegations as small as possible and that funeral invitations are limited ideally to the head of state and their spouse, without their family or staff.

It said the government “regrets that, because of limited space at the state funeral service and associated events, no other members of the principal guest’s family, staff or entourage may be admitted”.

The guidance adds: “The royal funeral unit would therefore be grateful if accompanying delegations can be kept as small as possible. This will also reduce disruption and transit time at airports. Where possible, overseas representatives should plan to arrive in the UK at least one day before the state funeral or the first event, which they are attending.”

It also says Heathrow will not be available for private flight arrangements or aircraft parking and says heads of state should use other London airports if they cannot fly commercially. It says the government will decline the use of helicopter transport because of the sheer volume of guests.

The guidance also advises foreign leaders that “it will not be possible to display flags at any airport for arrival or departure”.

London’s streets are unable to cope with the volume of private cars of foreign leaders expecting to attend the funeral. Instead, they will be taken to a separate site in London where the government will “provide coach transport from a central assembly point … Because of traffic restrictions, it will not be possible for guests to travel to such events in their own vehicles.”

The guidance tells visiting leaders that they can record short messages as they sign messages of condolence but there will be “no Autocue or makeup facilities”.

The foreign secretary, James Cleverly, will host a reception for all the international visitors attending the state funeral immediately after it concludes, close to Westminster Abbey.