Is my ex legally responsible to pay half the mortgage on our house even though he has moved out?

My ex partner moved out of the home we jointly mortgaged together in 2007, I took on full responsibility of the mortgage and paid this all on my own, never asked him for a penny towards the mortgage or for upkeep of the property. I paid him £10k at the time he moved out for part of his share of the property.

We sold the house recently and he is now asking for £7500 even tho we only sold the property making a £24k profit, which should be split fairly down the middle and seeing as he has had £10k already he should received a further £2k. I think I am being more the reasonable giving him half of the sale proceeds seeing as I have paid in the region of £40k mortgage payments over the last 7 years and he hasn't contributed a penny towards the house in this time.

He is refusing to allow the sale proceeds to be released and I am sat with nothing while he has had his £10k and is quibbling over getting his hands on £5k more than he is entitled. If it were to go further would I be legally entitled to get him to pay me back mortgage payments from what he hasn't paid over the last 7 years as he doesn't seem to be playing fair when I have been more than fair on the subject, I feel he is dragging his heels as he thinks if he holds things up long enough I will change my mind and give in to what he wants?

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