"Our president is happy to go by bus if told so, but he's over 80, so if there's a way to avoid it, we will try," another diplomat was quoted as saying.
Another added: "FCDO told us not to have many expectations, not to be too ambitious, and expect different problems. The logistical challenge is huge ... They're trying to convince us to take the buses, saying it's much easier to manage everything."
According to The Times, fears of gridlock on the roads around the Abbey, Houses of Parliament and Buckingham Palace necessitated the move to deploy buses.
Only two people allowed
The dignitaries, totalling over 2,000, mostly from across the Commonwealth of Nations, were instructed that their maximum allocation of seats was restricted to the head of state or their representative plus partner.
To control crowds, 36 kilometres of barriers were erected in central London alone, according to AP.
AP added that 5,949 military personnel have been deployed throughout the meticulously choreographed operation that began with the queen's death on September 8 at her Balmoral Estate in the Scottish Highlands.
Queen Elizabeth II, UK's longest-serving monarch, died on September 8, at Balmoral, Scotland aged 96. She will be laid to rest in a private ceremony in King George VI Memorial Chapel at Windsor Castle.