Somentimes airline companies denies boarding to some air passegers. This can be due to the practice of overbooking when air companies sell or book a greater number of tickets in comparison of the seats available on board. The consequence of overboking is that some air passengers lose their flight.
There are also further reason of denied boarding, e.g.:
If the air companies deny You boarding, You are entitled to get the a compensation (monetary compensation) between EUR 250 (about 210 GBP) and EUR 600 (about 510 GBP) per person.
Specifically, the compensation is 250 € for routes less than 1500km, 400,00 € for routes between 1500km and 3.500km and 600.00 € for routes more than 3.500km.
Besides of the compensation for the denied boarding, You can choose to get by the airline company alternatively:
You also have the right to be assisted by the airline company with:
If the company doesn't provide to offer You these services You can claim to be refunded of the substained expenses.
If you have suffered material, moral or existential damages (e.g. the loss of a vacation day), You have the right to get additional compensation besides the monetary one.
If your flight is part of a "all inclusive" holiday package the denied boarding may affects the success of the holiday. In such cases, the tour operator may be required to compensate You for holiday damage.