Under no circumstances would this be allowed. I would ask him verbally & politely to remove the wall & soil within 7 days as it could create a lot of problems for you with dampness.
If this is not done within the period, send him a registered letter with your grievances & reasons & hold him fully responsible for any damage to your property. Also inform him that you will take legal action & hold him fully responsible for all solicitors legal fees & court expenses if it go's this far .
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