James Hewitt, ex-lover of Diana, Princess of Wales, has been released on bail after being arrested on suspicion of possessing cocaine.
James Hewitt is a Gulf War veteran
TV and radio presenter Alison Bell, 37, who was held on suspicion of supplying a Class A drug, has also been bailed.
They are both due to return to a police station in September.
Mr Hewitt, 46, was arrested on Wednesday night after officers went to a bar in south west London, following a call to the police.
He could face a possible jail sentence of up to seven years if he is convicted of the offence.
If convicted, Ms Bell could face a maximum sentence of life in prison.
Mr Hewitt is a former army captain and veteran of the 1991 Gulf War.
In 1999 he published a book about his romantic liaison with the princess and about his experiences fighting in the Gulf.
Last December he was attacked in some sections of the media when he said he would sell love letters she had written to him.
Mr Hewitt first met Diana at a party in London's Mayfair in 1986. She was 25, he 28.
At the time, her marriage was in crisis and she and Prince Charles were in the middle of a 39-day separation.
Diana engaged Mr Hewitt as a riding instructor for both her and, later, her young sons.
Their affair, which began in 1987, ended in 1992, when the princess stopped taking his telephone calls.
The son, and grandson, of army officers, Mr Hewitt trained at Sandhurst Military Academy before being commissioned in the Life Guards.
He commanded A Squadron, Scots Guards, in the 1991 Gulf War.