Arsenal F.C.:

Expansion of Highbury was restricted because the East Stand had been designated as a Grade II listed building and the other three stands were close to residential properties. These limitations prevented the club from maximising matchday revenue during the 1990s and first decade of the 21st century, putting them in danger of being left behind in the football boom of that time. After considering various options, in 2000 Arsenal proposed building a new 60,361-capacity stadium at Ashburton Grove, since named the Emirates Stadium, about 500 metres south-west of Highbury. The project was initially delayed by red tape and rising costs, and construction was completed in July 2006, in time for the start of the 2006–07 season. The stadium was named after its sponsors, the airline company Emirates, with whom the club signed the largest sponsorship deal in English football history, worth around £100 million; some fans referred to the ground as Ashburton Grove, or the Grove, as they did not agree with corporate sponsorship of stadium names. The stadium will be officially known as Emirates Stadium until at least 2028, and the airline will be the club's shirt sponsor until the end of the 2018–19 season. From the start of the 2010–11 season on, the stands of the stadium have been officially known as North Bank, East Stand, West Stand and Clock end.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". When did Arsenal offer a plan to build a new stadium at Ashburton Grove?
2000