Deputy Prime Minister

The office of Deputy Prime Minister is one that has only existed occasionally in the history of the United Kingdom. Unlike analogous offices in other nations, the Deputy Prime Minister does not have any of the powers of the Prime Minister in the latter's absence and there is no presumption that the Deputy Prime Minister will succeed the Prime Minister.

The post has existed intermittently and there have been a number of disputed occasions as to whether or not the title has actually been conferred.

More from wikipedia: http://en.wikipedia.org/wiki/Deputy_Prime_Minister_of_the_United_Kingdom

Cabinet

The cabinet is the group of twenty or so (and no more than 22) senior government ministers who are responsible for running the departments of state and deciding government policy.

It is chaired by the prime minister.

The cabinet is bound by collective responsibility, which means that all its members must abide by and defend the decisions it takes, despite any private doubts that they might have.

Cabinet ministers are appointed by the prime minister and chosen from MPs or peers of the governing party.

However, during periods of national emergency, or when no single party gains a large enough majority to govern alone, coalition governments have been formed with cabinets containing members from more than one political party.

War cabinets have sometimes been formed with a much smaller membership than the full cabinet.

From time to time the prime minister will reorganise the cabinet in order to bring in new members, or to move existing members around. This reorganisation is known as a cabinet re-shuffle.

The cabinet normally meets once a week in the cabinet room at Downing Street.