(Reuters) – A 36-year-old runner who took part in the London Marathon on Sunday has died after he collapsed during the race, organisers said on Monday. The runner from Southeast England, who was not named by organisers, collapsed after the 23-mile mark. “Although he received immediate medical treatment and an ambulance was on the scene within three minutes, he died later in hospital,” organisers said in a statement. “The family has requested privacy and no further details will be released in accordance with their wishes. The cause of death will be established later through medical examination….