The postbox, which has seen the tree slowly grow around it, is in Roath, Cardiff
London Plane tree was planted as a sapling and now stands at 120ft tall
The Grade II listed postbox has now been decommissioned by Royal Mail chiefs
Royal Mail has been forced to block customers using an historic post box for the first time in 120 years because it is being swallowed by a tree.
Postmen citing 'health and safety fears' have refused to collect mail from the Grade II-listed red pillarbox in Roath, Cardiff, due to the London Plane looming overhead as it envelops it.
The tree, which started life as a sapling after it was planted to line the road as large homes were built between 1891 and 1910, has grown over more than a century to slowly consume the box.
The postbox has now been decommissioned by Royal Mail chiefs.
A sign on the box reads: 'Regrettably Royal Mail has had to remove this posting box from service as, due to the growth of the tree and the raised pavement, it is no longer safe to collect mail from.
'There are alternative posting boxes a short distance away.'
The nearest postbox is less than a half-mile away.
Local councillor Sue Lent said: 'The postbox has always been there and the tree wasn’t always so far around it. It wasn’t like that years ago.
'The postbox was certainly well used in the past.'
The box was located on Ninian Road, which is named after former MP for Cardiff Lord Ninian Creighton-Stuart.
Lord Creighton-Stuart was the son of landowner the 3rd Marquis of Bute.
He was killed in the First World War.
The Bute family owned the houses on the street and building work began on the road in 1891, which was finally finished in 1910, and trees were planted to line the road.
The London Plane now stands at more than 120ft tall.
There are conservation policies to keep the oldest and rarest letter boxes in their community.