Missing pages of lease d

I am buying a flat. But on the land registry, there are 6 missing pages of lease deed. They confirmed with the property manager all the flats in the block got identical lease . 

So, How can the missing pages put into the seller’s flat lease? 

 

Lok Yan Lung - you can't add copies of pages from another lease to one that's missing it's pages. You would either need to locate the original/counterpart/certified copy of the lease itself, perhaps held by the landlord or tenant and provide that to update the scanned copy we hold.
If neither the landlord or tenant have a complete copy of the lease then you should consider a deed of variation to correct the mistake or create a new lease and determine (close) the old one when registering the new one as appropriate.
Do speak to your conveyancer to confirm what the facts are re who holds what and see which solution is right for you as a purchaser

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Thank you for your replying. 
how long will it takes for the deed of variation or create a new lease ? 

Lok Yan Lung - once an application is submitted to register it it can then be expedited. Expedition means it is usually processed within 2 weeks but everything then hinges on it being in order.
So it's important to discuss that with your conveyancer. I imagine that getting the landlord and current tenant (seller) to complete a deed may take longer