Before Adebola murdered Irons, the court heard colleagues had become concerned by his behaviour towards her.
On 15 October, he purchased two knives “in order to kill” Irons.
Days later, he went to her home armed with a knife and inflicted a number of cuts to her as well as the fatal blow to the front of her neck.
The court heard after attacking her, Adegbola sat on the sofa “as she lay dead, or dying”.
He then left taking with him her phone and her keys, locking her inside before fleeing and disposing of his shirt, trousers and the murder weapon on his way.
“What you did on that day was to take the life of a young girl who was compassionate and accomplished and whose only fault was to love you at one time,” the judge said.
Adegbola handed himself into the police on 22 October, after feeling to Hull, and later pleaded guilty to murder in January.