What is the meaning of "To lift the UN1"

[youngken]

I am an overseas investor of a UK offplan property. I had paid 60% of price of my property and the rest will be paid upon completion.
However, the developer has encountered some financial difficulty and probably to be liquidated and left the partly built structure become unfinished.
I have received some document from my conveyance lawyer said " ... to lift UN1 "
What is that means?

 

[realdeals]

This is the description I found on the internet:-

"A unilateral notice can be most commonly found in the charges register of the property if it is registered. This notice is a charge used to register any interest which a third party may have in a particular property or estate, and notify the other party of its existence. "