How to remove entire row based on duplicates from single column in libre calc?

I have a table of 10 - 15 columns with 7000 rows containing a lot of data I have one column that contains a lot of duplicates, call it column N and I want to delete the entire row where the data is duplicate in row N and also i want to keep one of the rows, and only remove the duplicates.

I can highlight the duplicates and filter them but this takes way too long…

I cant use the “remove duplicates” button either because this only removes “duplicate rows”, not rows that have duplicates in a particular column.

Can somebody help me.

OP: @rea

Adding a extra column with a formula like:
copy down up the last row with data.
This formula resuls in value > 1 for the duplicated rows.
Filtering by this column for a non 1 value, shows all duplicated rows.

it doesn’t work…
but thanks anyway

Works perfectly, just need to make sure the cell references are correct.