Question: From when the British pub chain is owning the Flask public house who also operates nearly 220 pubs?

Context paragraphs:
Tynemill: Tynemill is a British pub chain based in the East Midlands and Yorkshire.  It was founded in 1977 by former Campaign for Real Ale (CAMRA) chairman Chris Holmes.  Their first pub was the "Old King Arms" in Newark.  Tynemill has won the "Pub Group of the Year" award in 2002, 2006, and 2008.

Büchner flask: A Büchner flask, also known as a vacuum flask, filter flask, suction flask, side-arm flask or Kitasato flask, is a thick-walled Erlenmeyer flask with a short glass tube and hose barb protruding about an inch from its neck.  The short tube and hose barb effectively act as an adapter over which the end of a thick-walled flexible hose (tubing) can be fitted to form a connection to the flask.  The other end of the hose can be connected to source of vacuum such as an aspirator, vacuum pump, or house vacuum.  Preferably this is done through a trap (see below), which is designed to prevent the sucking back of water from the aspirator into the Büchner flask.

Sizzling Pubs: Sizzling Pubs, also known as Sizzling Pub Company, is a British chain of pub restaurants, owned by Mitchells & Butlers (former Bass), that operates mainly as a steakhouse.  After Vintage Inns, it is M&B's most populous pub chain.

Half Moon, Herne Hill: The Half Moon is a Grade II* listed public house at 10 Half Moon Lane, Herne Hill, London.  It is one of only 270 pubs on the Campaign for Real Ale's National Inventory of Historic Pub Interiors, was frequented by the poet and writer Dylan Thomas, and was a noteworthy live music venue for nearly 50 years, hosting three gigs by U2 in 1980.  The Half Moon Public House is listed by Southwark Council as an Asset of Community Value. , and is described by Nikolaus Pevsner as, ""a cheerful corner pub of 1896"".

The Flask, Hampstead: The Flask is a Grade II listed public house at 14 Flask Walk, Hampstead, London, on the site from where the trade in Hampstead mineral water was run, and which is mentioned in the eighteenth century novel "Clarissa".  It has been owned by Young's Brewery since 1904.

The Flask, Highgate: The Flask is a Grade II listed public house at 74–76 Highgate West Hill, Highgate, London.  According to the 1936 "Survey of London", a pub known as The Flask has stood on this spot since "at least as early as 1663".  The present buildings probably date from the early 18th century, and were partially rebuilt in about 1767 by William Carpenter.  A Manorial court met there in the eighteenth century.  The Flask is currently owned and operated by the London-based Fuller's Brewery.

Pub quiz: A pub quiz is a quiz held in a pub or bar.  These events are also called quiz nights or trivia nights and may be held in other settings.  Pub quizzes may attract customers to a pub who are not found there on other days.  The pub quiz is a modern example of a pub game.  Although different pub quizzes can cover a range of formats and topics, they have many features in common.  The pub quiz was established in the UK in the 1970s by Burns and Porter and became part of British culture.  The Great British Pub Quiz challenge is an annual event.

Yates's: Yates is a British pub chain, founded as Yates Wine Lodge in Oldham, Lancashire by Peter and Simon Yates in 1884.  The chain remained strongest in the North of England, though spreading nationwide.

Pub chain: A pub chain is a group of pubs or bars with a brand image.  The brand may be owned outright by one company, or there may be multiple financiers; the chain may be a division within a larger company, or may be a single operation.  Examples include Chef & Brewer, Wetherspoons, Walkabout, Taylor Walker Pubs and All Bar One.  Pubs in the chain are typically branded with the same name, however the former "Firkin" pubs tended to be variations on a theme including the word Firkin in the title.  Wetherspoons pubs have individual names, with the Wetherspoons brand prominently displayed.

Young's: Young's (Young & Co.'s Brewery Plc) is a British pub chain operating nearly 220 pubs.

Supporting paragraphs: The Flask, Hampstead Young's
Answer: 1904