A Tory MP who appeared to fall asleep in the House of Commons has said he is embarrassed and "annoyed" with himself.
Sir Desmond Swayne, who nodded off during a speech by colleague Ken Clarke, said the image of him with his head on his shoulder was "horrible".
In his defence, he said he had had a "very long day", having been up swimming in London at 05:30 GMT.
"I dozed off for 30 seconds," he told BBC 5 live. "That is the extent of it. It happened. It won't happen again."
Sir Desmond, who is a supporter of Brexit, nodded off during the 11th day of debate on the EU Withdrawal Bill but rejected suggestions he was making a statement about Mr Clarke's pro-Remain views.
The New Forest West MP said he had heard Mr Clarke's speech before but his "momentary lapse" was not because he was "bored" with proceedings but was a result of tiredness.
"I was listening to Ken Clarke and I felt woozy," he told Emma Barnett. "Then all of a sudden you have gone for 30 seconds. I am annoyed I let it happen. It is embarrassing and annoying."
The 61-year old said he had started the day in question "very early" with a dip in the Serpentine, a lake in London's Hyde Park, before dawn.
The afternoon nap was later referred to when Sir Desmond was called to ask a question at Prime Minister's Questions - where he was greeted with loud cheers from the Tory benches.
“The Rt Hon Gentleman is extremely alert!” jokes the Speaker— BBC Daily Politics and Sunday Politics (@daily_politics) January 17, 2018
“A question keeps me awake at night” says @DesmondSwayne asking the PM about Iceland
The #pmqs question came 24 hours after he was not listening too attentively to Ken Clarke: https://t.co/FMXeNJpvKO pic.twitter.com/z2UMGnVxtR
When he was a soldier, Sir Desmond - who served in Iraq in 2003 - said he had taught himself to "catnap" because of the limited opportunities for repose.
"I am sure everyone has experienced that feeling when you are really tired and you just feel yourself going," he told Emma Barnett.
"I have a very long day. I have a great deal to do. Most people have busy lives and busy jobs and I'm sure they've experienced it as well."
As debate on the EU bill resumed in the Commons on Wednesday, Mr Clarke said he was glad to see Mr Swayne sitting behind him again.
"When I arrived I inquired whether he'd had a cup of coffee before today's long proceedings," he said, adding that he was trying to have "no soporific effects" on those MPs who had "survived" the lengthy discussions on the Bill.
Speaking on 5 live, fellow Conservative MP Bernard Jenkin said it was "not good to be seen to be asleep on the job".
However, he said he had sympathy for his colleague as it was "pretty easy to feel droopy" after a busy day and given the rather close atmosphere in the chamber.
He joked that in the days before Commons proceedings were first televised in 1989, MPs used to go into the Chamber for a nap.
"It's only the advent of television that means you can't go in to the House of Commons and have a snooze."
But Labour's Chuka Umunna questioned whether people who were unable to stay awake in the Commons should remain as MPs.