This from the BBC article:
A worker in the immigration department at Heathrow, who asked not to be named, said the situation was chaotic. "It's a mess. We cannot deploy without breaching health and safety measures. We are short staffed anyway. What are you meant to do?"
Lucy Moreton, general secretary of ISU, the union for Borders and Immigration, said the queues were caused by Covid restrictions imposed by Border Force, which is part of the Home Office. She said that staff have been put into bubbles of 10 people to reduce the risk of cross infection, but that this prevents more staff being deployed when the border becomes busy.
"Staff are very upset about the measure," said Ms Moreton. "They have been receiving verbal abuse as the queues have got longer. "The measure is not necessary, it contributes to the queues and it doesn't stop infection as staff have to interact outside those bubbles in other areas of the site," she said.
The Home Office called these comments "disingenuous" and said that the ISU had previously acknowledged that zonal working provides benefits to health and safety.
The ISU disputes this, saying it had never said that the measure has any benefits. It said the measure adds nothing material to Covid security for staff, but impairs their ability to respond to demand.
I have met the ISU Gen Sec a couple of times - I believe her rather than their overlords. Not least as, over the past decade, we have seen under staffing in normal times. It is my personal view that the Govt has deliberately under staffed to save money for a long time.