A fragment of the True Cross, recognised by the majority of Catholic and Greek Orthodox movements, will arrive amid tight security at the Holy Church of Saint Panteleimon and Saint Paraskevi, in Kenton, on Thursday.
Thousands of followers are expected to flock to the Kenton Road church to pray to and touch the religiously significant relic, which many believe possesses healing powers.
The sacred object has been flown over from Jerusalem with its own security team by the Greek Orthodox Archdiocese in central London for a UK-wide tour.
Clergymen at the Harrow church are preparing for the wooden cross’s early-morning arrival, which is causing a hubbub of excitement in the local community.
Parish priest at the church, Anastasios Salapatas, said: “This is one of the most significant events in my ministerial life of almost 30 years.
“It is a very special moment in the history of our community, particularly from a spiritual point of view, and we count it as a blessing that it is coming to us.”
Some historians say the True Cross was discovered by Saint Helen in Jerusalem when she travelled to the Holy Land in 326-328AD.
Many churches around the world possess fragments purported to be the remains of the True Cross, though its authenticity is not widely recognised by all Christian faiths.
The Orthodox faith has in the region of 10,000 followers in the Harrow and Brent region and large numbers, including many with illnesses and ailments are expected to carry out pilgrimages from across the south east to get a glimpse of the cross.
The Holy Church of Saint Panteleimon and Saint Paraskevi is preparing its own security around the priceless piece, and special religious services will be held in Greek and Romanian for congregations throughout the day.
Father Salapatas said: “The cross is recognised as the most important Christian symbol around the world and we’re expecting a huge crowd.
“The whole thing is generating a lot of emotion among people – they have contacted us wanting to touch it and have their prayers answered.
“We’re very excited and everyone is looking forward to its arrival. We feel very blessed.”