Basic earnings per share are calculated by dividing the profit attributable to ordinary shareholders by the weighted average number of ordinary shares in issue during the period. The weighted average number of shares excludes shares held by an Employee Benefit Trust (see note 23) and has been adjusted for the issue/purchase of shares during the period.

For diluted earnings per share, the weighted average number of ordinary shares in issue is adjusted to assume conversion of all dilutive potential ordinary shares. These represent share options granted to employees where the exercise price is less than the average market price of the Company's ordinary shares during the 52 weeks to 31 March 2017.

The Group has also chosen to present an alternative earnings per share measure, underlying earnings per share, with profit adjusted for non-recurring items because it better reflects the Group's underlying performance. This measure is defined on Our Key Performance Indicators.

For the period52 weeks to
31 March 2017
Number of shares
m
52 weeks to
1 April 2016
Number of shares
m
Weighted average number of shares in issue199.1199.1
Less: shares held by the Employee Benefit Trust (weighted average)(2.5)(3.9)
Weighted average number of shares for calculating basic earnings per share196.6195.2
Weighted average number of dilutive shares0.51.1
Total number of shares for calculating diluted earnings per share197.1196.3
For the period52 weeks to
31 March
2017
£m
52 weeks to
1 April 2016
£m
Basic earnings attributable to equity shareholders56.463.5
Non-recurring items (see note 5):
Operating expenses3.41.7
Finance costs0.6
Tax on non-recurring items(0.9)(0.3)
Underlying earnings before non-recurring items59.564.9

Earnings per share is calculated as follows:

For the period52 weeks to
31 March
2017
52 weeks to
1 April
2016
Basic earnings per ordinary share28.7p32.5p
Diluted earnings per ordinary share28.6p32.4p
Basic underlying earnings per ordinary share30.3p33.2p
Diluted underlying earnings per ordinary share30.2p33.0p