Sources at the Saint Thomas hospital says Boris Johnson has breathing difficulties.
He was given 4-litre of oxygen to stabilise.
In an interview this morning , Michael Gove, a government minister also confirmed that Boris is not on a ventilator and that he was admitted into intensive care unit at about 7:00 pm last night.
Johnson, 55, had not been intubated , a procedure where a tube is inserted into the windpipe before ventilation — but needed four litres of oxygen in intensive care, sources at the hospital said.
The normal threshold for intensive care is 15 litres, suggesting that he was in better health than such patients generally.