Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
Britain's Got Talent
Table title:
Judges
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=2 > Series </th><th colspan=4 rowspan=1 > Main Judge </th><th colspan=1 rowspan=2 > Guest Judge </th></tr>
<tr> <th colspan=1 rowspan=1 > 1 </th><th colspan=1 rowspan=1 > 2 </th><th colspan=1 rowspan=1 > 3 </th><th colspan=1 rowspan=1 > 4 </th></tr>
<tr> <th class="highlighted"  colspan=1 rowspan=1 > 1 </th><td class="highlighted"  colspan=1 rowspan=13 > Simon Cowell </td><td class="highlighted"  colspan=1 rowspan=13 > Amanda Holden </td><td class="highlighted"  colspan=1 rowspan=4 > Piers Morgan </td><td colspan=1 rowspan=4 > N/A </td><td colspan=1 rowspan=2 > N/A </td></tr>
<tr> <th class="highlighted"  colspan=1 rowspan=1 > 2 </th></tr>
<tr> <th class="highlighted"  colspan=1 rowspan=1 > 3 </th><td colspan=1 rowspan=1 > Kelly Brook </td></tr>
<tr> <th class="highlighted"  colspan=1 rowspan=1 > 4 </th><td colspan=1 rowspan=2 > Louis Walsh </td></tr>
<tr> <th colspan=1 rowspan=1 > 5 </th><td colspan=1 rowspan=1 > Michael Mcintyre </td><td colspan=1 rowspan=1 > David Hasselhoff </td></tr>
<tr> <th colspan=1 rowspan=1 > 6 </th><td colspan=1 rowspan=8 > Alesha Dixon </td><td colspan=1 rowspan=8 > David Walliams </td><td colspan=1 rowspan=1 > Carmen Electra </td></tr>
<tr> <th colspan=1 rowspan=1 > 7 </th><td colspan=1 rowspan=1 > N/A </td></tr>
<tr> <th colspan=1 rowspan=1 > 8 </th><td colspan=1 rowspan=1 > Ant & Dec </td></tr>
<tr> <th colspan=1 rowspan=1 > 9 </th><td colspan=1 rowspan=1 > N/A </td></tr>
<tr> <th colspan=1 rowspan=1 > 10 </th><td colspan=1 rowspan=1 > Kathleen Walliams </td></tr>
<tr> <th colspan=1 rowspan=1 > 11 </th><td colspan=1 rowspan=3 > N/A </td></tr>
<tr> <th colspan=1 rowspan=1 > 12 </th></tr>
<tr> <th colspan=1 rowspan=1 > 13 </th></tr>
</table>
Question:
Who were the Britain's Got Talent judges for the first four series?
Answer:
Britain's Got Talent judges for the first four series were Simon Cowell, Amanda Holden, and Piers Morgan.