Malcom Graham, 75, of Skegness Road, Stevenage, took advantage of his friendship with a woman, sexually assaulting her in her own home while she slept in 2018.
The victim disclosed the offence to Bedfordshire Police in 2019, and an investigation was launched.
Detective Sergeant Amy Hawkes from Bedfordshire Police said: “This was a predatory attack by a man who posed as a friend to prey on a woman in her own home.
“During the investigation, Graham denied the incident was non-consensual stating, ‘she did not say no’.
“However, consent means agreeing to what’s happening by choice and having the freedom and ability to make or change that choice. During the incident, some people may feel pressured, scared and they may even freeze, which makes them unable to make a free choice, and that is still a crime.
“I want to thank the victim for finding the courage to come forward and for remaining supportive of the investigation over several years. I would also like to extend my thanks to her husband for the unwavering support he has shown her.
“This case demonstrates convictions are possible for sexual assaults, no matter who the offender is, when they took place or when they were reported.’’
Victims of rape and sexual assault can receive support and guidance from Bedfordshire Police and its partner agencies, including the Sexual Assault Referral Centre (SARC) and Bedford Domestic Abuse Partnership (BDAP), as well as support through the criminal investigation process.