Using RegEx to remove RTF formatting

Transact-SQL
2

I have tried this just to get out one of the common lines '\pard\plain\plain\fs24\par' using this syntax, that I think is right:

use [exoMashTrust-test]

select 
	sql#.RegEx_Replace(
	pati.THENOTES
	,'\pard\plain\plain\fs24\par'
	,''
	,1
	,1
	,null
	)

from
 PATIENT_INCIDENTS as pati

But I get this error:

Msg 6522, Level 16, State 1, Line 3
A .NET Framework error occurred during execution of user-defined routine or aggregate "RegEx_Replace": 
System.ArgumentException: parsing "\pard\plain\plain\fs24\par " - Malformed \p{X} character escape.
System.ArgumentException: 
   at System.Text.RegularExpressions.RegexParser.ParseProperty()
   at System.Text.RegularExpressions.RegexParser.ScanBackslash()
   at System.Text.RegularExpressions.RegexParser.ScanRegex()
   at System.Text.RegularExpressions.RegexParser.Parse(String re, RegexOptions op)
   at System.Text.RegularExpressions.Regex..ctor(String pattern, RegexOptions options, TimeSpan matchTimeout, Boolean useCache)
   at System.Text.RegularExpressions.Regex..ctor(String pattern, RegexOptions options)
   at REGEX.Replace(SqlChars ExpressionToValidate, SqlString RegularExpression, SqlString Replacement, SqlInt32 Count, SqlInt32 StartAt, SqlString RegExOptionsList)
.

I have no idea what this means.