qgis – Regex substr – Extracting number after specific text sequence

Couldn’t find any solution to a specific sequence.
Context: italian cadaster, where plot number is embedded in a table coded in kml, in the “description” field. I want to extract the plot number.

Part of the code is:

...<tr>

<td>SVILUPPO</td>

<td>25</td>

</tr>

<tr bgcolor="#D4E4F3">

<td>NUMERO</td>

<td>156</td>

</tr>

<tr>

<td>LIVELLO</td>..."

In this example, I want to get: 156. There are other categories (commune, cadastral sheet, etc., with other numbers. I need to identify the right number quoting “NUMERO”.

Tried:

regexp_substr(  "description" , 'NUMERO</td> \n\n <td>(\\d+)<' )

regexp_substr(  "description" , 'NUMERO \\D+ (\\d+) <' )

With:

‘NUMERO as the start of the sequence,
\D+ as any non decimal character,
(\d+) to extract subchain with any number
< to close the sequence.

Both formulas are valid, but I get ‘NULL’ in return. I can’t see why.
Any help much welcome.