Hi, thank you foe your question. Just a bit more information required to fully assist you:
-Are you in England or Wales?
-Are/were you married?
-Who gave permission and was this under a court order?
-Were the items bought by him?
Thanks for confirming. He would have committed a trespass by entering the property without your permission but if he took items that he bought and are his solely, then it will be difficult to attempt to pursue him for this.
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Were they solely paid for and purchased by him?
Thanks for confirming. Firstly you should contact the police on their non-urgent line (101) as taking things that are not his and entering the home without your permission are criminal offences. If they cannot recover the items or assist, you should write a formal letter to him requesting their return by a certain date, after which you should pursue a court application to your local county court for the court to make an order - you can do this using form N1 and a £355 court fee.