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:
Senedd
Table title:
Timeline of cost increases and time delays
Table:
<table id='hittask' contenteditable='False'>
<tr> <td colspan=1 rowspan=1 > Construction period </td><td colspan=1 rowspan=1 > Date </td><td colspan=1 rowspan=1 > Estimated and final cost </td><td colspan=1 rowspan=1 > Estimated completion date </td><td colspan=1 rowspan=1 > Notes </td></tr>
<tr> <td colspan=1 rowspan=5 > Phase 1 including selection processes </td><td class="highlighted"  colspan=1 rowspan=1 > July 1997 </td><td class="highlighted"  colspan=1 rowspan=1 > c£12M </td><td colspan=1 rowspan=1 > April 2001 </td><td colspan=1 rowspan=1 > The first estimate by the Welsh Office in the A Voice for Wales white paper. </td></tr>
<tr> <td colspan=1 rowspan=1 > 16 October 1998 </td><td colspan=1 rowspan=1 > £11.6M (total) £8.4M (construction) </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > RRP estimated cost at time of the design selection process. </td></tr>
<tr> <td colspan=1 rowspan=1 > January 2000 </td><td colspan=1 rowspan=1 > £22.8M </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Revised estimate by RRP after changes to the design of the building by the National Assembly. </td></tr>
<tr> <td colspan=1 rowspan=1 > March 2000 </td><td colspan=1 rowspan=1 > £26.7M </td><td colspan=1 rowspan=1 > January 2003 </td><td colspan=1 rowspan=1 > Estimate produced by Turner and Townsend for the National Assembly. </td></tr>
<tr> <td colspan=1 rowspan=1 > May 2001 </td><td colspan=1 rowspan=1 > £37M – £47M (total) £28M (construction) </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Estimate from a 3-day workshop by the National Assembly and all contractors involved in the project. </td></tr>
<tr> <td colspan=1 rowspan=5 > Phase 2 </td><td colspan=1 rowspan=1 > September 2001 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > July 2004 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > January 2003 </td><td colspan=1 rowspan=1 > £29.3M (construction) </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Estimate from Taylor Woodrow, Schal and Northcroft, which was based on an incomplete design. </td></tr>
<tr> <td colspan=1 rowspan=1 > 30 May 2003 </td><td colspan=1 rowspan=1 > £41M (construction) </td><td colspan=1 rowspan=1 > August 2005 </td><td colspan=1 rowspan=1 > Tender submission by the Taylor Woodrow Strategic Alliance Partnership after value engineering. </td></tr>
<tr> <td colspan=1 rowspan=1 > July 2003 </td><td colspan=1 rowspan=1 > £66.1M (total) £48.2M (construction) </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > The final construction lump sum offer made by the Taylor Woodrow Strategic Alliance Partnership. </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 7 February 2006 </td><td class="highlighted"  colspan=1 rowspan=1 > £69.6M (final total cost) £49.7M (final construction cost) </td><td colspan=1 rowspan=1 > Completion date </td><td colspan=1 rowspan=1 > The total project cost, including £7.5M from phase 1. </td></tr>
<tr> <td colspan=2 rowspan=1 > 1 March 2006 (Royal opening ceremony) </td><td class="highlighted"  colspan=3 rowspan=1 > The project was 580% over budget compared with the original budget forecast in April 1997 (phase 1) and was four years and 10 months late. </td></tr>
<tr> <td colspan=7 rowspan=1 > Sources: National Audit Office Wales, Accommodation Arrangements for the National Assembly for Wales and Wales Audit Office, The Senedd </td></tr>
</table>
Question:
How much did the cost of the Senedd increase by from 1997 to 2006?
Answer:
The cost of the Senedd increased from £12M in 1997 to £69.6M in 2006, an increase of 580%.