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:
Joyce Smith
Table title:
Achievements
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Year </th><th colspan=1 rowspan=1 > Competition </th><th colspan=1 rowspan=1 > Venue </th><th colspan=1 rowspan=1 > Position </th><th colspan=1 rowspan=1 > Event </th><th colspan=1 rowspan=1 > Notes </th></tr>
<tr> <th colspan=6 rowspan=1 > Representing Great Britain and England </th></tr>
<tr> <td colspan=1 rowspan=1 > 1971 </td><td colspan=1 rowspan=1 > International Cross Country Championships </td><td colspan=1 rowspan=1 > San Sebastián, Spain </td><td colspan=1 rowspan=1 > 3rd </td><td colspan=1 rowspan=1 > 4.5 km </td><td colspan=1 rowspan=1 > 11:24 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1972 </td><td colspan=1 rowspan=1 > International Cross Country Championships </td><td colspan=1 rowspan=1 > Cambridge, United Kingdom </td><td colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > 4.5 km </td><td colspan=1 rowspan=1 > 16:11 </td></tr>
<tr> <td colspan=1 rowspan=1 > Olympic Games </td><td colspan=1 rowspan=1 > Munich, Germany </td><td colspan=1 rowspan=1 > 12th (sf) </td><td colspan=1 rowspan=1 > 1500 m </td><td colspan=1 rowspan=1 > 4:09.4 </td></tr>
<tr> <td colspan=1 rowspan=1 > 1973 </td><td colspan=1 rowspan=1 > World Cross Country Championships </td><td colspan=1 rowspan=1 > Waregem, Belgium </td><td colspan=1 rowspan=1 > 2nd </td><td colspan=1 rowspan=1 > 4 km </td><td colspan=1 rowspan=1 > 13:58 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1974 </td><td colspan=1 rowspan=1 > World Cross Country Championships </td><td colspan=1 rowspan=1 > Monza, Italy </td><td colspan=1 rowspan=1 > 7th </td><td colspan=1 rowspan=1 > 4 km </td><td colspan=1 rowspan=1 > 13:04 </td></tr>
<tr> <td colspan=1 rowspan=1 > European Championships </td><td colspan=1 rowspan=1 > Rome, Italy </td><td colspan=1 rowspan=1 > 3rd </td><td colspan=1 rowspan=1 > 3000 m </td><td colspan=1 rowspan=1 > 8:57.39 </td></tr>
<tr> <td colspan=1 rowspan=1 > 1978 </td><td colspan=1 rowspan=1 > World Cross Country Championships </td><td colspan=1 rowspan=1 > Glasgow, United Kingdom </td><td colspan=1 rowspan=1 > 9th </td><td colspan=1 rowspan=1 > 4.7 km </td><td colspan=1 rowspan=1 > 17:23 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1979 </td><td colspan=1 rowspan=1 > Avon International Women's Marathon </td><td colspan=1 rowspan=1 > Waldniel, Germany </td><td colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:36:27 </td></tr>
<tr> <td colspan=1 rowspan=1 > Tokyo Marathon </td><td colspan=1 rowspan=1 > Tokyo, Japan </td><td colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:37:48 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1980 </td><td colspan=1 rowspan=1 > Avon International Women's Marathon </td><td colspan=1 rowspan=1 > London, United Kingdom </td><td colspan=1 rowspan=1 > 7th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:41:22 </td></tr>
<tr> <td colspan=1 rowspan=1 > Tokyo Marathon </td><td colspan=1 rowspan=1 > Tokyo, Japan </td><td colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:30:27 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 1981 </td><td class="highlighted"  colspan=1 rowspan=1 > London Marathon </td><td colspan=1 rowspan=1 > London, United Kingdom </td><td class="highlighted"  colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > Marathon </td><td class="highlighted"  colspan=1 rowspan=1 > 2:29:57 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=2 > 1982 </td><td colspan=1 rowspan=1 > Osaka International Ladies Marathon </td><td colspan=1 rowspan=1 > Osaka, Japan </td><td colspan=1 rowspan=1 > 5th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:35:34 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > London Marathon </td><td colspan=1 rowspan=1 > London, United Kingdom </td><td class="highlighted"  colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > Marathon </td><td class="highlighted"  colspan=1 rowspan=1 > 2:29:43 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1983 </td><td colspan=1 rowspan=1 > Osaka International Ladies Marathon </td><td colspan=1 rowspan=1 > Osaka, Japan </td><td colspan=1 rowspan=1 > 8th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:40:01 </td></tr>
<tr> <td colspan=1 rowspan=1 > World Championships </td><td colspan=1 rowspan=1 > Helsinki, Finland </td><td colspan=1 rowspan=1 > 9th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:34:27 </td></tr>
<tr> <td colspan=1 rowspan=2 > 1984 </td><td colspan=1 rowspan=1 > Nagoya International Women's Marathon </td><td colspan=1 rowspan=1 > Nagoya, Japan </td><td colspan=1 rowspan=1 > 6th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:38:55 </td></tr>
<tr> <td colspan=1 rowspan=1 > Olympic Games </td><td colspan=1 rowspan=1 > Los Angeles, United States </td><td colspan=1 rowspan=1 > 11th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:32:48 </td></tr>
<tr> <td colspan=1 rowspan=1 > 1985 </td><td colspan=1 rowspan=1 > Osaka International Ladies Marathon </td><td colspan=1 rowspan=1 > Osaka, Japan </td><td colspan=1 rowspan=1 > 7th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:38:09 </td></tr>
<tr> <td colspan=1 rowspan=1 > 1986 </td><td colspan=1 rowspan=1 > Osaka International Ladies Marathon </td><td colspan=1 rowspan=1 > Osaka, Japan </td><td colspan=1 rowspan=1 > 14th </td><td colspan=1 rowspan=1 > Marathon </td><td colspan=1 rowspan=1 > 2:42:36 </td></tr>
<tr> <th colspan=6 rowspan=1 > (sf) Indicates overall position in semifinal round </th></tr>
</table>
Question:
How many times did Joyce Smith win the London Marathon ?
Answer:
Joyce Smith won twice at the London Marathon, in 1981 with 2:29:57, and 2:29:43 in 1982.