v3.26.3
Share capital (Details)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Dec. 18, 2024
USD ($)
shares
Feb. 29, 2024
USD ($)
shares
Jun. 30, 2026
GBP (£)
Vote
item
shares
Jun. 30, 2025
GBP (£)
shares
Jun. 30, 2024
GBP (£)
shares
Jun. 30, 2026
$ / shares
Jun. 30, 2026
GBP (£)
shares
Ordinary shares              
Balance at the beginning | £     £ 56,000        
Issue of shares | £       £ 79,985,000 £ 158,541,000    
Balance at the end | £     £ 56,000 56,000      
Number of class of ordinary shares | item     2        
Number of class A shares to which one B share is convertible     1        
Proportion of affirmative votes required for special resolutions     66.67%        
Treasury shares | £       £ 21,305,000     £ 21,305,000
Trawlers Limited investment              
Ordinary shares              
Issue of shares | $ $ 100 $ 200          
Ordinary shares              
Number of shares              
Balance at the beginning (in shares)     174,112,000 171,001,000      
Balance at the end (in shares)     174,174,000 174,112,000 171,001,000    
Ordinary shares              
Balance at the beginning | £     £ 56,000 £ 55,000      
Balance at the end | £     £ 56,000 £ 56,000 £ 55,000    
Ordinary shares | INEOS Limited (now INEOS Services Limited) investment              
Number of shares              
Issue of shares (in shares)       3,030,000      
Ordinary shares              
Issue of shares | £       £ 1,000      
Ordinary shares | Employee share-based compensation awards              
Number of shares              
Issue of shares (in shares)     62,000 81,000      
Class A ordinary shares              
Number of shares              
Balance at the beginning (in shares)     57,763,582        
Balance at the end (in shares)     57,826,116 57,763,582      
Ordinary shares              
Par value per ordinary share (in dollars per share) | $ / shares           $ 0.0005  
Number of voting right per share | Vote     1        
Number of shares held in treasury             1,682,896
Treasury shares | £             £ 21,305,000
Class A ordinary shares | Trawlers Limited investment              
Number of shares              
Issue of shares (in shares) 983,450 1,966,899          
Class B ordinary shares              
Number of shares              
Balance at the beginning (in shares)     116,348,173        
Balance at the end (in shares)     116,348,173 116,348,173      
Ordinary shares              
Par value per ordinary share (in dollars per share) | $ / shares           $ 0.0005  
Number of voting right per share | Vote     10        
Percentage of ordinary shares outstanding below which Class B shares will convert to Class A     10.00%        
Percentage of voting power of shareholders     67.00%        
Class B ordinary shares | Trawlers Limited investment              
Number of shares              
Issue of shares (in shares) 2,046,854 4,093,707