Basic earnings per share is calculated by dividing the profit attributable to equity holders of the Company by the weighted average number of ordinary shares in issue during the period, excluding ordinary shares held pursuant to the Group's joint share ownership scheme ("JSOS") which are accounted for as treasury shares.

Diluted earnings per share is calculated by adjusting the weighted average number of ordinary shares outstanding to assume conversion or vesting of all dilutive potential shares. The Company has two (2015: two) classes of instruments that are potentially dilutive, namely share options and shares held pursuant to the JSOS.

Basic and diluted earnings per share has been calculated as follows:

52 weeks ended 27 November 2016
Number of shares (m)
52 weeks ended
29 November 2015
Number of shares (m)
Issued shares at the beginning of the period, excluding treasury shares590.6586.1
Effect of share options exercised in the period2.52.2
Effect of treasury shares disposed of in the period1.3
Weighted average number of shares at the end of the period for basic earnings per share594.4588.3
Potentially dilutive share options and shares19.131.1
Weighted average number of diluted ordinary shares613.5619.4
£m£m
Profit attributable to the owners of the Company 12.0 11.8
pencepence
Basic earnings per share2.022.01
Diluted earnings per share1.961.91