Officers conducting a raid next door to the enthusiast's home were caught off guard when they saw the military memorabilia through the window. This led to the arrest of the 52 year old collector under section 5 of the 1968 Firearms Act.
However, after hours in custody, he was released without charge around 5pm once police deemed the weaponry "ornamental".
The history buff expressed his distress to The Oxford Mail, saying he felt "upset" after being apprehended for firearms offences due to his display of a Second World War grenade on his windowsill.
Wishing to remain anonymous after being handcuffed in front of his neighbours, he complained about the way he was handled: "I said from the start, I can look inside them (the grenades)," he explained, "There is nothing inside them."
He continued: "They are trained officers so how could they not tell? If they just listened to what I was saying it could have been solved then."
After taking him to the station, Thames Valley Police quickly realised the weapons were merely decorative pieces. Recalling his ordeal, he said: "They did not even know what they were charging me with when I was there.
"They were halfway through doing my fingerprints when they said they could release me."
A history enthusiast, who has a keen interest in "wars throughout history", amassed his collection from various antique shops across London, valuing it at several hundred pounds.
The assortment featured items such as a German Stielhandgranate stick grenade, a Soviet Union F1 Fragmentation grenade, and bullets for numerous historical firearms, including a Kalashnikov automatic rifle.
Following his arrest, the collector's mother is quite displeased and has suggested he file a complaint. However, his primary concern is the return of his collection.
"Most of all I want my stuff back," he declared.
Moreover, the police seized his keys to access his property, which have yet to be returned to him.
He claims that apart from being given a crime number, he has not been informed about how to retrieve his belongings.
He commented: "I think they were just doing their job, but I think they could have dealt with it a lot better."
He also mentioned that the custody sergeant offered an apology for the inconvenience caused and provided him a lift home in a police vehicle.
A spokesperson for Thames Valley Police (TVP) clarified: "The munitions on further investigation were found to be ornamental hand grenades which were not live and were not illegal."
Consequently, the man arrested was released without any charges.
The operation on Marlborough Road was executed by nearly a dozen officers, including armed personnel and a police K9 unit.