John Browne was the group chief executive of BP from 1995 to 2007. He is seen as the person largely responsible for the BP policies which are now the cause of considerable concern for their environmental impact, as evidenced in the letter (20 April) signed by 160 people from the art world, including myself. Tate director Nicholas Serota has rejected such calls on the basis that "you don't abandon your friends because they have what we consider to be a temporary difficulty". The Tate has issued a statement that BP fits within the guidelines set out in its sponsorship and ethics policies. Serota is employed by the Tate board of trustees, chaired by Browne, who surely can carry no credibility for overseeing in this instance the application of Tate's ethical policies, which are effectively a judgment on his own career.
Charles Thomson
Co-founder, The Stuckists
• In my attack on Oxford University's poor record on admitting black students (Letters, 14 April) I inadvertently insulted the entire university staff by referring to their "titanic salaries". I would like to stress that I meant only the very senior management staff of the university itself. Most academics – let alone administrators – are paid remarkably little.
Robin McGhee
St Anne's College, Oxford
• Well done to the Lee Valley White Water Centre people for opening a year ahead (Report, Sport, 20 April). The sailing facility in Portland and Weymouth was in use last year, by sports bodies and the public. Credit where it is due?
AR Martin
Swindon, Wiltshire
• Greek word, four syllables, starts with H (Letters, 20 April)? I have to admit with a psi that I give up. The question is getting on Minervas.
Terri Green
Langley, Warwickshire
• Sorry, Jane Sutherland (Letters, 20 April), a pair of Kyles cuckoos, one on Bute, one over here, 15 April.
Anne Archer
Tighnabruaich, Argyll
• Cuckoo heard 9 April in woods above Nazeing, Essex.
Carol Clark
Troon, Ayrshire