Ramdev's spokesman SK Tejarawala described as "baseless" that he was being questioned on carrying some medicines.
"It was not clear why the Yoga guru was detained for over six hours at Heathrow. He was not carrying anything with him except a small bag of personal effects. It is for the British authorities to explain why he was detained," Tejarawala told PTI.
He said Ramdev has been cleared to go into the city.
Ramdev went to London to attend a function organised by the Patanjali Yogpeeth on the 120th anniversary of Swami Veivekanand in the next couple of days.