Plus: the longest delay for any new stadium in history and the worst goal difference you can get away with and still qualify in the Champions League. Mail us or tweet @TheKnowledge_GU

“Real Madrid recently lost 3-0 to Eibar in a stadium that holds just 7,000 people,” begins Robin Tucker. “That got me thinking: have any former European champions lost a competitive match in a smaller stadium? This would be only counting results after their first European success, so games such as Liverpool’s 1959 defeat to Worcester City would not count.”

A fine question, but it’s not even the smallest stadium a former European champion has lost in this season. The 1986 winners Steaua Bucharest, now snappily known as FCSB, have suffered plenty of turmoil recently, including a defeat earlier this month to Sepsi OSK. That was in front of an estimated 2,500 at the 5,200-capacity Stadionul Municipal.

Still, now we’ve ruined that one, here are some more. Nottingham Forest were beaten before 4,284 hardy souls at Burton Albion earlier this season, and Adam Wilson has others: “18 October 2005, Johnstone’s Paint Trophy, Woking 3-2 Nottingham Forest – attendance 3,127; 3 December 2005, FA Cup second round, Chester 3-0 Forest – attendance 4,732; 21 August 2006, League Cup first round, Accrington Stanley 1-0 Forest – attendance 2,146.”

Facebook Twitter Pinterest Paul Mullin of Accrington celebrates after scoring against Forest in 2006. Photograph: Alex Livesey/Getty Images

Boris Cule writes: “I’d like to nominate Aston Villa’s defeat at Slaven Belupo in the 2001 Intertoto Cup. I’m not sure what the stadium’s capacity was at the time, but it’s probably safe to assume it wasn’t much higher than its current 3,134.”

And here’s Liam McGuigan on The Shock of Gibraltar: “Celtic’s 1-0 defeat at Lincoln Red Imps in the 2016-17 Champions League was played at the Victoria Stadium, which has a capacity of around 2,300. On the international front (hey, the question didn’t specify!), Greece’s 2-1 defeat to Faroe Islands in Euro 2016 qualifying was held at Tórsvøllur, which holds about 6,000.”

Any more for any more? Email knowledge@theguardian.com.

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Grounds for concern

“How long is the longest delay for a football stadium to open after its original published opening date, and how does the new Spurs stadium compare?” tweets Dave Waghorn.

Dave du Vergier is right out of the blocks and looks back 12 years: “Valencia’s Nou Mestalla must be a front-runner here – they are still waiting to move in.” Marca reported last year that: “Work on the arena to the north-west of the city centre began in 2006 but was abandoned three years later due to financial issues, however a pre-existing agreement with the local council that Los Che must vacate the current Estadio Mestalla by 2023 remains in place.”

Facebook Twitter Pinterest The Nou Mestalla Stadium, pictured here in 2010, a year after it was due to open. It hasn’t progressed much further since. Photograph: Manuel Queimadelos Alonso/Getty Images

And there’s more …

PremPlace (@PremPlace) Dublin's Shamrock Rovers may be up there with this one. Work commenced to build Tallaght Stadium in October 2000. Because of a couple of issues, the stadium lay half built for years. They eventually played their first game on March 13, 2009. https://t.co/BPqllCmp4g

… and more …

Хардкуна Матата (@sviraman) Krestovsky Stadium in St. Petersburg was originally planned to open in late 2008, in fact was completed in April 2017 (and then additional touchups continued up until the World Cup)

Accentuate the negatives

“If Shakhtar beat Lyon by one goal in the final round of Champions League fixtures in December,” writes Oscar Clarke, “they will qualify for the knockout stage with a goal difference of -7. Has any team ever qualified, or even won their group, with a worse goal difference record?”

In short, no. The next worst qualifiers were Galatasaray, who came second in their 2013-14 group with a -6 goal difference. But more teams than you might think have made it through scoring fewer than they conceded: 25 in total, since groups were introduced in 1994-95. The only teams to win a group with a negative goal difference were Valencia in 2002-03 (the second group phase, impressively) and Sturm Graz in 2000-01. The latter was an odd one all round: both they and Galatasaray qualified with goal differences of -3, whereas Rangers and Monaco slunk home on +3.

The best performing side who qualified in the red was PSV, who recovered from posting -1 in 2004-05 to reach the semi-final, beaten there by Milan. Each and every one of the other 24 lucky sides went out at the next stage of the competition they faced.

Knowledge archive

“Many years ago I read a story somewhere about a ‘crazy’ supporter in South America who shot a ball that was flying into the goal with a pistol to stop the goal being scored,” recalled Illya McLellan in 2016. “Apparently the ball fell to the ground and didn’t go in. I have tried to find out if this story was true and wondered if anyone else had heard of it?”

According to our mate Google, this story was included in Bizarre World, Bill Bryson’s 1995 bitesize ode to the kookiness of mankind. It also resides in the memory bank of Connor Bogdanovic. “I’m a contributor to RSSSF (Australian State Leagues),” wrote Connor, coincidentally sharing his favourite chat-up line. “My eyes lit up when I saw this question. Amazingly, I came across this in the Canberra Times while researching a tournament from 1978:

It did not occur in South America, but on the island of Corsica, in France. On 23 April 1978, one Jean-Marc Luccheti took a trip to watch his side, Calenzana, play against Murato, in a local league match. During the game, a shot from one of the Murato players was heading towards the goal.

The Murato player, as you well know from perusing the question, was not the only one with a shoot-on-sight policy. “Our hero was not having it,” continued Connor. “He quickly drew a pistol and shot the ball, deflating or popping it and preventing the ball from going in. Luccheti was later arrested and attempted to persuade law enforcement that he only shot blanks. It proved unsuccessful. He admitted to the crime and was sentenced to three months in jail.”

• For thousands more questions and answers look through our archive.

Can you help?

“What is the earliest point in a game that a goalkeeper has gone up for a corner or free-kick?” asks Kirsty McGregor.

“The recent Port Vale v Stoke City U21s Checkatrade Trophy match has been jokingly referred to as ‘El Ceramico’,” begins Derrick Cameron. “Along with more famous examples such as the ‘Old Firm’, ‘El Clásico’ and the ‘Superclásico’, what other derby games are known by their nicknames rather than by a location?”

“As Kilmarnock went top of the Scottish Premiership, I looked them up on Wikipedia,” writes Paul Savage. “Kilmarnock has a population of 46,350. Rugby Park holds 17,899. My maths makes that their stadium can hold 38% of the town. Are there any other high-flying clubs that dominate their respective populace?”

jeremyorbell (@jeremyorbell) Back in the 80s @LincolnCity_FC always seemed to play at home on Boxing Day while @theposhofficial were away - doesn't seem to apply these days but it did back then. What's the longest run of home or away fixtures on the 26th December?

“What is the longest Boxing Day football trip a team has had to make?” enquires David Gregson.

“I couldn’t help but notice all the names in the Arsenal squad on Saturday that would be impossible to remember how to spell in a football quiz. Lots of Ks and Xs and Zs,” writes Phil Grey. “However, there was no J, Q or V, so I’m wondering if a match-day squad, or even a starting 11, has had all the letters of the alphabet in it. First names don’t count.”

Email your questions and answers to knowledge@theguardian.com or tweet @TheKnowledge_GU. It’s the Christmas special next week …