The Holy Grail is located in London, Hounslow to be precise

An article in Fortean Times says a certain Barrie-Jon Bower, who is said to be an amateur archaeologist, claimed to have found the Holy Grail. According to him it is in a crypt under a river in Hounslow in the west of London.

Mr. Bower, of Cinderford, Gloucestershire, is convinced that the cup Jesus drank from during The Last Supper remained hidden in the West London suburbs for hundreds of years. He claims the Knights Templar trained on Hounslow Heath before embarking on their crusades. He says they built a secret crypt to hide the seized relics and that the ‘entrance was subsequently hidden.

He had found a thousand pounds to hire geophysical equipment to scour the land but had to apply for permission to drain the river from the Environmental Agency. Now we know they received this request and were considering it, but there has been no other news for months. Many legends say that the Holy Grail was brought by the Crusaders to England, generally one thinks of places like Glastonbury, Hounslow is new. We are waiting for news from Hounslow then.

The Holy Grail is presumably the cup from which Jesus drank at the Last Supper and which Joseph of Arimathea used to collect the blood of Jesus when he was crucified. Some Arthurian accounts state that Joseph of Arimathea brought the Holy Grail in Glastonbury in England and buried it there. Others believe that the Knights Templar took the Holy Grail from the Temple Mount during the Crusades and brought it back to England, where they hid it. The search for the Grail has become the most holy of searches, as it offers both union with God and eternal youth, wealth and happiness to all who drink it.