Plus: high-scoring defenders (2); Losing to stay up; Four and out (2); and Eidur Gudjohnsen and his dad. Send your questions and answers to knowledge@guardian.co.uk

"Is there any evidence of a city derby record equal or better than the 22 games undefeated Heart of Midlothian went against Hibernian in Edinburgh?" wonders Ewan Murray. "The first game was 1 April 1989, last 30 April 1994."

In two-team cities, Ewan, we've failed to top Hearts' efforts, north or south of the border. The longest runs we can find in Scotland, using Soccerbase's excellent head-to-head search facility, are Rangers' 12-match streak over Celtic between 1960 and 1964, and Dundee United's 16-match unbeaten run against their city rivals between 1979 and 1984.

In England, the longest runs in two-team cities we've found are:

Manchester Utd 16 matches from February 1990 to April 2001

Liverpool 15 matches from March 1972 to April 1978

Aston Villa 13 matches from November 1887 to October 1904

Sheffield Wednesday 11 matches from October 1910 to October 1919

Bristol Rovers 10 matches from April 1986 to January 1991

Nottingham Forest eight matches from September 1923 to October 1928

Stoke v Port Vale have produced a couple of six-match runs (the latest, Port Vale's, is still ongoing)

In London, though, Hearts' record is smashed. "Chelsea went undefeated against Spurs for 26 matches in all competitions starting with their 3-2 victory on 1 Dec 1990 and lasting until their 2-1 win on 9 January 2002," writes Nate Elliott. "Better yet, when they finally lost to Tottenham in 2002, it was in the League Cup - if you ignore the cups and count only league matches [which we won't - Knowledge Ed], Chelsea's dominance lasted a full 32 matches, again starting on 1 Dec 1990 and lasting through their 2-1 victory on 11 March 2006."

Can anyone beat that anywhere from Antwerp to Zurich? Get in touch at the usual address.

KOEMAN, HIERRO .... AND NOW GANNON

"I was wondering who has been the highest goalscoring defender in a season," wrote Barkat Ahmed last week. "I remember Marco Materazzi scoring 12 goals in one season for Perugia. Can anyone beat that?"

We've answered this before, but it's certainly worth an update in the light of new information. For anyone to lazy to click on the link, back in 2003 we listed Ronald Koeman (PSV) and Fernando Hierro (Real Madrid) as sharing the record with 21 goals apiece in a single season, while Steve Bruce (Manchester United) and Derek Mountfield (Everton) were tied for third with 19 goals each.

But no longer. Hierro and Koeman have to replace their golden crowns for bronze ones and find room for Stockport's Jim Gannon. "Gannon was (and still is) known by Stockport fans as 'The Ghost', due to his knack of 'ghosting' in at the back post to score from crosses," writes Stephen Shawcross of the central defender who scored 21 times in all competitions in 1991-92.

The new kings of the goalscoring defenders are River Plate's Daniel Passarella and AFC Wimbledon's Matt Everard. "Passarella, the former Argentina captain, scored 24 league goals during the 1976 season," writes Iain Biglin. He went on to hit double figures in three further seasons in South America and even managed 11 goals in Serie A in 1985-86.

Charlie Talbot and Matt West write to fill us in on the details of Everard's achievement. "Not top-level admittedly but at AFC Wimbledon we had a rather prolific centre-back who scored 24 in a season when we won the Combined Counties League," writes Matt. "He was actually the third top scorer. Sixteen of them came in the league. Matt Everard was his name, he joined us from Ash United after reading a fan's website and eventually turned down a move to Aldershot to stay with the club until injury cut his career short. He, was, and is, a legend and a top man."

LOSING TO STAY UP

"After a discussion with a friend in the pub the other day I was reminded of a story I once heard on a phone-in one Saturday afternoon. While I forget the details I remember hearing about a team who had found themselves in the position where on the last day of the season they needed to lose the game to stay up. Can this be true?" demanded Andrew Law last week.

Let's hand things over to Ciaran Grant: "This put me in mind of when the Irish League decided to split in two in order to form the Irish Premier League during the 1990s. It was decided that the eight best teams would be decided by taking their average league position over the course of two seasons. Roll on the final day of the season in April 1995. Coleraine and Bangor both shared 8th position on average and both had local derbies to play against Ballymena and Ards respectively. Coleraine had the upper hand as they were in 7th position and Bangor were 11th.

"What the IFA hadn't thought of, though, was this: Ards were one point behind Coleraine so if Coleraine failed to win their match and Ards won against Bangor then Ards would move above Coleraine pushing their average down slightly, meaning Bangor would have a better average and it would be them that would go into the new Premier League. And guess what – this is exactly what happened. At half time Ards lead Bangor 1-0 and Coleraine v Ballymena was scoreless. In the second half Ards scored again (to the cheers of the Bangor fans) and ran out 2-0 winners. If I recall correctly Bangor didnt exactly try in the second half. Coleraine and Ballymena ended 0-0 and thus although Bangor lost it was they that stayed in the top flight."

FOUR AND OUT (2)

Last week we looked at the teams to score four away goals and still exit a competition. Sean DeLoughrey writes in with a few more:

• Luxemborg's finest, F91 Dudelange, lost 2-1 at home and 5-4 away to Slovakia's MSK Zilina in the 2007-08 Champions League qualifiers.

• PSV Eindhoven lost 5-4 away and 5-4 on aggregate to Bayer Leverkusen in the 94-5 UEFA Cup.

• Zeljeznicar Sarajevo lost 5-4 away and 9-7 (!) on aggregate to Anderlecht in the 70-1 FAIRS Cup.

• Grasshoppers drew 4-4 at NK Croatia in the 97-8 UEFA Cup before crashing 5-0 at home.

KNOWLEDGE ARCHIVE

"I heard that Chelsea striker Eidur Gudjohnsen once played alongside his own dad up front for Iceland." says Kai from Norway. "Is this true?"

Once upon a time there was an Icelandic footballer called Arnor Gudjohnsen. At 25 he was asked his biggest wish, to which he replied "to play international football alongside Eidur."

At this point his eight-year-old son, a young lad with shockingly blonde hair arranged in the tousled fashion that gave him that just-out-of-bed look, emerged from behind his legs. "It was always the dream."

A dream that sadly never came true. A match against Estonia in 1996 was the closest they ever came, when, after 62 minutes, Arnor was substituted by 17-year-old debutant, Eidur. For a brief, kiss-on-the-cheek moment, the two were on the pitch at the same time. History was written.

But in a twist of fate cruel enough to make you think half of England's monarchical ancestry was up there pulling the strings, shortly before a match in Reykjavik in which father and son were scheduled to appear alongside one another, young Eidur broke his ankle in an under-18 tournament. He duly missed the next two seasons, in which time Arnor hung up his boots and bought a fishing rod.

"It remains my biggest regret that we didn't get to play together, and I know it's Eidur's too" said Arnor. Come on now, we're sure we remember some skied efforts from three yards out that should weigh slightly heavier on his mind.

For more heartwarming sepia-tinged questions and answers, take a trip through the Knowledge archive.

Can you help?

"Following Joey Barton's red card on Sunday it occurred to me that six players have been sent off for challenges on Xabi Alonso this season already. Would this be anywhere near a record for a season?" wonders Eoin Dowling. "Has another player been on the wrong end of more red card challenges?"

"Last Saturday Tonbridge Angels took on Dover Athletic in the Isthmian Premier in a game notable for it's lengthy first half. First of all Tonbridge player, Lee Browning, was hit by the ball and knocked out, requiring 26 minutes of treatment on the pitch. There was soon another lengthy delay as referee Stephen Child hobbled off with an injury with the linesman replacing the referee and a replacement linesman being needed. As well as those two incidents, the Tonbridge keeper was also sent off, a Dover centre-back was sent off, and both managers were also sent off. By the time the half-time whistle was blown it was 4.28pm with the first half lasting 87 minutes. Has there ever been more stoppage time in a match than that?" asks Ben Stagles.

"Are Birmingham City the first club to win a 'hat-trick' of successive promotions from the Championship, ie, in their last three seasons in the divisions – 2002, 2007, 2009 – go up?" asks Dave Ryan. "And would they do so scoring the fewest number of goals by a promoted side?"

What team, and which player, holds the record for the shortest time between winning a league championship and getting relegated?" ponders Scott Cuthbert. "Has any team ever been relegated the year after lifting the trophy? (Not including relegations for rule-breaking)."

"Brentford were promoted to League One on Saturday but there's a debate going on about whether any team has been promoted as Champions without their manager winning a single manager-of-the-month award during the season?" writes Tony Cross. "Also we didn't apparently have a single player good enough for the PFA Team of the Season — is the combination unique?"

Send your questions and answers to the lovely people at knowledge@theguardian.com