Table:
text: Administrative counties of England
Area and population
Area and population
Administrative_County Area_statute_acres_1891 Population_1891 Area_statute_acres_1961 Population_1961 Headquarters
Huntingdonshire 233928 54969 233985 79924 Huntingdon
Isle of Ely 239259 63861 239951 89180 March
Isle of Wight 93342 78672 94142 95752 Newport
Kent 971849 785674 971125 1671436 Maidstone
Lancashire 1124450 1768278 1060804 2280359 Preston
Leicestershire 520400 200468 515404 409098 Leicester until 1967, Glenfield thereafter
Lincolnshire – Parts of Holland 255252 75522 267847 103327 Boston
Lincolnshire – Parts of Kesteven 471749 105910 462100 134842 Sleaford
Lincolnshire – Parts of Lindsey 961327 199095 961038 505427 Lincoln
London 75442 4232118 74903 3200484 Spring Gardens until 1933, Lambeth thereafter
Middlesex 149046 560012 148691 2234543 Westminster
Monmouthshire 342548 203347 339008 336566 Newport
Norfolk 1303967 317983 1302505 388005 Norwich

Question: What is the population n1891 of the county headquartered in Sleaford in the counties of England?