Blockbusters was originally an American show that aired from 1980-1982, and again briefly in 1987. However, the show was vastly more popular and successful in the UK, where in ran from 1983 to 1994. Sadly the host for that show, Bob Holness, passed away last year. The show was also revived last year in the UK as The All New Blockbusters.
The show had a very odd format, in that, with the exception of the '87 season of the US version, it always pitted a team of two players against a single opponent. The game board also had a unique design, consisting of a grid of 20 interlocking hexagrams. The object of the game was to gain control of tiles that bridge two opposing sides of the board. For the single player this meant bridging the top and bottom, while for the duo it meant bridging the sides. Because of the layout of the board, the single player could do this with only four tiles, while the team needed at least 5. In the US version, the team was always a pair of relatives (though never husband and wife). In the UK version, all of the contestants were always sixth form students (what in the US would be considered 11th and 12th graders).
Each round would begin with a toss up question that would determine who chooses the first tile. From then on whoever gave the last correct answer chooses a tile, and anyone can ring in at any time during the reading of the clue to attempt to provide the correct answer. If they fail to do so, the other side gets a chance to answer. If neither side gets it, another clue will be read in it's place. The correct answer for any given tile always starts with the letter on the tile, and the players specify which tile they choose by it's letter. So it's always 20 different letters. Wikipedia claims that X and Z are never used, and yet oddly enough, in the video I posted you can clearly see an X on one of the tiles.
The match is best out of three rounds. Once one side wins twice, that contestant, or one of the pair of contestants gets to play the bonus round, called the Gold Run. In this they have sixty seconds to form a side to side bridge. Instead of single letters, each tile contained two or more letters, which are the abbreviation of the multi-word answer for that tile. And that's pretty much it. After the Gold Run, a new contestant/pair would be brought in and the game would start over. Because of this, episodes could span multiple matches, and could begin and/or end in the middle of a match. Reigning champions could stay on the show for up to 5 consecutive matches (reduced to 3 in some seasons).