Modify RDL Definition Using SQL

Question

Hi I'm trying to modify over 100 ssrs rdl files to include some standard text in the report header so i thought the easiest option would be to modify the rdl definition in the reportserver database where i've ran into 2 issues

1. when my new XML includes <rd:DefaultName>ReportPrivacyLabel</rd:DefaultName> i get the following error which must be related to namespace not sure how to resolve this

XML parsing: line 24, character 17, undeclared prefix

2. when <rd:DefaultName>ReportPrivacyLabel</rd:DefaultName> is not included in the new XML my sql query doesn't modify my rdl xml

Any advice would be greatly appreciated

DECLARE @myDoc XML;  
SET @myDoc = N'
<Report MustUnderstand="df" xmlns="http://schemas.microsoft.com/sqlserver/reporting/2016/01/reportdefinition" xmlns:rd="http://schemas.microsoft.com/SQLServer/reporting/reportdesigner" xmlns:df="http://schemas.microsoft.com/sqlserver/reporting/2016/01/reportdefinition/defaultfontfamily">
      <df:DefaultFontFamily>Segoe UI</df:DefaultFontFamily>
      <ReportSections>
        <ReportSection>
          <Page>
            <PageHeader>
              <Height>1.75543cm</Height>
              <PrintOnFirstPage>true</PrintOnFirstPage>
              <PrintOnLastPage>true</PrintOnLastPage>
              <ReportItems>
              
                <Textbox Name="ReportName">
                  <CanGrow>true</CanGrow>
                  <KeepTogether>true</KeepTogether>
                  <Paragraphs>
                    <Paragraph>
                      <TextRuns>
                        <TextRun>
                          <Value>=Globals!ReportName</Value>
                          <Style>
                            <FontSize>16pt</FontSize>
                          </Style>
                        </TextRun>
                      </TextRuns>
                      <Style />
                    </Paragraph>
                  </Paragraphs>
                  <rd:DefaultName>ReportName</rd:DefaultName>
                  <Top>0.30903cm</Top>
                  <Left>0.5842cm</Left>
                  <Height>0.83283cm</Height>
                  <Width>12.63883cm</Width>
                  <Style>
                    <Border>
                      <Style>None</Style>
                    </Border>
                    <PaddingLeft>2pt</PaddingLeft>
                    <PaddingRight>2pt</PaddingRight>
                    <PaddingTop>2pt</PaddingTop>
                    <PaddingBottom>2pt</PaddingBottom>
                  </Style>
                </Textbox>
                
                <!-- THIS IS WHERE I WANT TO INSERT NEW XML -->
              
              </ReportItems>
              <Style>
                <Border>
                  <Style>None</Style>
                </Border>
              </Style>
            </PageHeader>
            <PageFooter>
              <Height>1.35467cm</Height>
              <PrintOnFirstPage>true</PrintOnFirstPage>
              <PrintOnLastPage>true</PrintOnLastPage>
              <Style>
                <Border>
                  <Style>None</Style>
                </Border>
              </Style>
            </PageFooter>
            <PageHeight>29.7cm</PageHeight>
            <PageWidth>21cm</PageWidth>
            <LeftMargin>2cm</LeftMargin>
            <RightMargin>2cm</RightMargin>
            <TopMargin>2cm</TopMargin>
            <BottomMargin>2cm</BottomMargin>
            <ColumnSpacing>0.13cm</ColumnSpacing>
            <Style />
          </Page>
        </ReportSection>
      </ReportSections>
    </Report>'
    
    DECLARE @newFeatures XML;  
    SET @newFeatures = N'
    <Textbox Name="ReportPrivacyLabel">
        <CanGrow>true</CanGrow>
        <KeepTogether>true</KeepTogether>
        <Paragraphs>
            <Paragraph>
                <TextRuns>
                    <TextRun>
                        <Value>Secret and Confidential</Value>
                          <Style>
                            <FontStyle>Normal</FontStyle>
                            <FontFamily>Consolas</FontFamily>
                            <FontWeight>Normal</FontWeight>
                            <TextDecoration>None</TextDecoration>
                            <Color>Red</Color>
                          </Style>
                    </TextRun>
                </TextRuns>
                <Style>
                    <FontSize>10pt</FontSize>
                </Style>
            </Paragraph>
        </Paragraphs>
        <rd:DefaultName>ReportPrivacyLabel</rd:DefaultName>
        <Top>1.15543cm</Top>
        <Left>0.5842cm</Left>
        <Height>0.6cm</Height>
        <Width>6.77567cm</Width>
        <ZIndex>1</ZIndex>
        <Style>
            <Border>
                <Style>None</Style>
            </Border>
            <PaddingLeft>2pt</PaddingLeft>
            <PaddingRight>2pt</PaddingRight>
            <PaddingTop>2pt</PaddingTop>
            <PaddingBottom>2pt</PaddingBottom>
        </Style>
    </Textbox>'; 
    
    SET @myDoc.modify('
    insert sql:variable("@newFeatures") as last          
    into (/Report/ReportSections/ReportSection/Page/PageHeader/ReportItems)[1] ')             
    SELECT @myDoc;  
    GO