The 18lb mortar was found by Dave Pearce, a magnet fisherman from Roundhay who was fishing under Crown Point Bridge in Leeds on Friday, March 29.
Mr Pearce's friend Ian Platt, who was also fishing, said: "We posted the photos online and within two minutes he got a reply saying it’s probably a mortar bomb - get out of there.”
Police were called shortly after 11am and Crown Point Bridge and the stretch of canal underneath it, where the bomb was, were cordoned off.
- > Teenager stabbed as two seriously injured after fight between two groups in Potternewton Park, LeedsThe bomb squad arrived at around 2.30pm and identified the device, previously thought to be from World War Two, as a live Boer War mortar.
The Boer War was fought between the British Empire and two Boer states between 1899 and 1902, making the device almost 120 years old.
After cutting through a gate to allow better access to the scene, Army officials then lifted the bomb into the back of a wagon filled with sandbags.
It was thought a controlled explosion would take place in situ however at 3.40pm, the mortar was driven away from the scene for a controlled explosion.
It was reported at the scene the bomb was taken to East End Park in Leeds to be disarmed.
West Yorkshire Police said on Twitter: "For those in the area of East End Park, Leeds: Within the next few minuets there will be a controlled explosion in the area.
"Do not panic. Police are aware and directly involved and dealing with the situation."