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My property is mentioned on the Land Registry as freehold , but under the charges there is a 999yr lease mentioned.
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If a lease is mentioned in the charges register, then it is likely that the lease is something your property is subject to - ie that a lease has been granted over your freehold. There are other explanations for this, but to be honest your solicitor shoudl be able to explain to you the issue - what is the exact wording entry in the charges register?
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I am currently in the process of selling my property, but my buyers solicitor has said he will not buy with the 'Defective Title' and wants it sorting. My solicitor has applied to the Land registry for any old documents they may have to shed light on how this may be resolved, but she is not confident she can sort this.
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If you have an indemnity policy covering the point, then you are probably prevented under the terms of the policy from investigating this further to the extent that such investigation brings matters to the attention of whoever the beneficiary is of the charge. Why is the buyer not comfortable with the insurance policy?