Wellington boots will be allowed at this year's Henley Royal Regatta, with organisers relaxing the normally strict dress code because of the wet weather.
Thousands are expected to line river banks during the regatta
Organisers of the famous rowing event on the Thames, which starts on Wednesday, have also stepped up security this year.
The annual five-day rowing regatta is held over a stretch of the River Thames on the Oxfordshire/Berkshire border.
Extra security measures are in place due to the heightened state of alert.
Organisers said 467 crews from 18 nations, including South Africa, Canada, Slovenia, Greece, Czech Republic, USA, Australia and New Zealand will take part.
First held in 1839, the Henley Royal Regatta has been held every year except during the world wars.