Bill Clinton and Monica Lewinsky embraced, made out and had sex in just about every nook and cranny of the Oval Office.

Secret Service officer Gary Byrne should know. He's the man who stood guard outside Bill Clinton's Oval Office, was the last obstacle to Monica Lewinsky's access to the President.

And the White House intern, Byrne says, was relentless in her pursuit of the President.

'What (if anything) she did all day as an intern mystified me. Some days she seemingly had nothing better to do than play I Spy the President', Gary Byrne writes in his bombshell book Crisis of Character: A White House Secret Service Officer Discloses His Firsthand Experience with Hillary, Bill, and How They Operate to be published by Center Street Books on June.28.

'Monica hung around us batting her eyes until she overheard the president's position or direction of travel, then bolted to maneuver into his path. She lived for even his passing glance.'

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Ex-Secret Service officer Gary Byrne was posted outside Bill Clinton's Oval Office during the Clinton administration. Monica Lewinsky had special access to the Oval Office for at least two years

When dogging the President down off-limit hallways, she had a playbook of lame excuses, he writes:

'I'm just here to use the bathroom; You mean I have to walk all the way around?; They asked me to deliver something here; I'm just here to see a friend'; were only a few.

Gary Byrne says he was posted outside Bill Clinton's Oval Office in the 1990s and what he saw 'sickened him'

When she saw Byrne, she tried sneaking in through neighboring offices and corridors – any way she could to get to Bill.

All the Secret Service had witnessed Bill and Monica 'embracing, making out, or on the Oval Office Desk'.

And she frequently wore dresses that were too short – anything to catch the president's eye.

On one occasion, after Clinton sighted her, 'she turned back to ensure she had his attention – and flipped up her black-and-white print dress to reveal her blue thong'.

Clinton laughed and said, 'Hey, there!'

One failed attempt was on a weekend when Bill was alone in the Oval Office and Monica appeared with news articles and his morning briefings.

Byrne was pissed because Clinton already had his briefings. He sent Monica on her way only to have Clinton come out and ask if someone had come by with files for him.

Byrne lied and responded 'no'.

Monica wasn't going to be sent away that easily.

She had slipped into the nearby Roosevelt Room and called the President to advise him that she had failed in her mission to reach the Oval Office.

Monica was actually able to direct dial the President without going through anyone.

'The president had provided Monica Lewinsky with access to his direct line'.

Agents witnessed Bill and Monica 'embracing, making out, or on the Oval Office Desk,' says ex-officer Byrne

Monica was transferred to the East Executive Building where there was no approach to the West Wing. Now she was a Social Office intern under Hillary Clinton

Byrne was just incensed to learn that Monica had the 'secret number' – 'so secret that it required not only a four-digit pass code but a rhythmically coded one'.

You had to depress keys for a specific length of time and there were precise pauses between numbers.

So irate at the 'behind-closed-doors-kind of relationship' the pair was carrying on, Byrne approached the Deputy Chief of Staff Evelyn Lieberman and asked that Monica be removed from the West Wing.

'I believe I have your – the administration's – best interest in mind', he told her.

The next day, Monica was transferred to the East Executive Building where there was no approach to the West Wing. Now she was a Social Office intern under Hillary.

'I do believe Mrs. Clinton knew of the affairs, but how did she feel about an affair with someone of her own daughter's age? And in the Oval Office? In plain sight of us? Still, I don't think she knew of Monica,' he surmises.

But Byrne's appeal to rid the Oval Office of Monica didn't work. Monica was more devious than Byrne initially gave her credit for.

Days later, Monica reappeared with her new pass. 'Look, I have a blue one now,' she told Byrne, that indicated she was now a paid presidential staffer.

Her salary was paid for with taxpayer dollars.

'Now the situation was even worse,' Byrne lamented. Monica was back - on the government dime.

Clinton worked his magic and pulled some strings to get his girl, 'the Blue Pass Princess', back in his arms.

Byrne was just incensed to learn that Monica had the President's 'secret number' – 'so secret that it required not only a four-digit pass code but a rhythmically coded one.' You had to depress keys for a specific length of time and there were precise pauses between numbers, he explains

Monica was always using Steward Nel as one of the people she needed to see and Nel warned her that she didn't want to end up like 'that Paul Jones girl'. Monica viewed herself as smarter than Paula Jones so that couldn't happen

Byrne didn't see the women as the problem. Clinton was the problem, he writes.

Details on Monica's affair came out in confessional conversations Lewinsky made to her confidante, Linda Tripp.

They had become pals - in Monica's mind only - when they worked together in the public affairs office at the Pentagon, where Monica was transferred after Byrne first consulted with Evelyn Lieberman and asked that she be removed.

Byrne, one of the officers who complained about Monica Lewinsky's behavior, says he wants voters to see the 'real' Hillary before they head to the polls

Lewinsky came back to the White House from the Pentagon with the blue pass as a paid staffer.

Monica confessed to Tripp that she had given oral sex to the president while he talked on the phone with ambassadors and other dignitaries.

And she revealed to Tripp the details of the semen-stained blue dress still in her possession.

'The staff kept aiding and abetting her and the president wanted her there,' Byrne writes.

'President Clinton paid for a White House mistress with taxpayer funds and jeopardized national security with her compromising and corruptible presence in a secure area, all for little more than on-demand oral sex.

'We thought we knew what was going on. We didn't know the half of it.

'Had I never recommended that Monica needed to leave, Monica would have never met Linda.'

And we would never have learned about the blue dress.

The stewards were usually the first to discover traces of every secret sexual liaison at 1400 Pennsylvania Avenue.

Monica was always using Steward Nel as one of the people she needed to see and Nel warned her that she didn't want to end up like 'that Paul Jones girl'. Monica viewed herself as smarter than Paula Jones so that couldn't happen.

In late 1996, one of Nel's discoveries was deeply disturbing to him.

'He'd been finding and cleaning semen and lipstick-stained towels for weeks.

'If the stains didn't rinse out, he'd carefully remove them by hand' - hand washing them himself.

Embarrassed for the presidency itself, he didn't want Navy laundry personnel to learn about the semen.

'F***ing Monica!' Byrne thought.

Monica confessed to LInda Tripp that she had given oral sex to the president while he talked on the phone with ambassadors and other dignitaries. And she revealed to Tripp the details of the semen-stained blue dress (above) still in her possession

But that wasn't Monica's lipstick stain on the towels. She didn't wear that color.

'I believed that this particular lipstick belonged to the current West Wing receptionist. I just knew it.'

Byrne guessed the receptionist wasn't wiping her mouth on the towels. The president was wiping semen and lipstick off of his penis.

'That was the key to the towels' that bore the White House seal.

Byrne was outraged that the Presidential Seal was violated in such a way. He wouldn't even walk across the Presidential Seal on the Oval Office carpet.

'The White House was where kings and queens, sheikhs and ambassadors met the world's most powerful leader,' he moaned.

'Pageantry was a business expense and SOP, Standard Operating Procedure.'

Byrne decided to take control of this issue.

He 'placed the offending linens' in a trash can liner and hid them near his post in a drawer until the end of the day. He took them home and then worried about illegally destroying evidence.

Clinton was a 'horndog' who 'had difficulty managing where he saw his many mistresses - at the White House or on the road'.

'It baffled the Uniformed Division as to how he could manage all these women without any of them realizing there were so many others.

'He would have been better at running a brothel in a red-light district than the White House.'

'So now she was pissed off. She pressed the officer about the delay and wanted to know why she was left standing in his security booth.'

When the officer gave her a vague excuse, Byrne writes, Lewinsky allegedly gestured at her own body and said: 'What's he want with her when he has this?'

'Lashed out': Monica Lewinsky got all-access from 1996, former Secret Service officer Gary Byrne claims. But in 1997 she allegedly had a tantrum at the gates when she realized Bill Clinton was with another woman

The scene is one of many explosive accusations against the Clintons.

Byrne describes his intimate connection to the president's private life.

'I stood guard, a pistol at my hip, outside the Oval Office, the last barrier before anyone saw Bill Clinton. The last barrier before Monica Lewinsky saw Bill Clinton. Yes, I'm that Secret Service officer,' Byrne writes.