Risks associated with confining fans in pens were highlighted by the Committee of Inquiry into Crowd Safety at Sports Grounds (the Popplewell inquiry) after the Bradford City stadium fire in May 1985.
Riscurile asociate cu închiderea fanilor în țarcuri fuseseră deja subliniate de către Committee of Inquiry into Crowd Safety at Sports Grounds (ancheta Popplewell) imediat după incendiul de la stadionul Bradford City din mai 1985.