He knows that already

"You're a fresh one. You have just asked me out on a date when you know my husband is watching from the other side of the pool." 

"I thought we were getting on so well and he hasn't said anything that perhaps he wouldn't mind if I took you out tonight.” 

“Why don’t you go over and ask him?” 

“And what would he say if I did.” 

“He would say, ‘Yes of course Master’.” 

“You’re kidding! Right?” 

“My Harvey understands the Natural Order. He sees it as an honour for his Wife to go on a date with a real man like yourself.” 

“Oh hey! He’s one of those cuckolds my friends told me about.” 

“Him and thousands of others just like him. Shall we go?” 

“Maybe I should tell him that I will look after you but you won’t be back until tomorrow.” 

“He’s a cuckold Master. He knows that already.”