I heard that it's always a good idea -regardless of your destination- to get a visa to the country you traveling to prior to your travel even if it was the case that you can get a visa upon arrival as you might get refused entry.
But I get the visa before traveling is there a chance that I could be refused entry ?
It is for the Israeli authorities to determine the right of entry into Israel, if you have any particular concerns about visas or entry into Israel, you should contact the Israeli Embassy in London.
So if the embassy said yes, airport officials wouldn't be able to say no?