Archibald Seth Armstrong was born in 1926 and grew up in Beckindale. He had a sister who later moved to Worthing. Seth romanced young Betty Prendagast in 1944 and they almost married. He later got married in 1952 to Meg and they had two children, Jimmy in 1953 and Freddie followed about 9 years later.
Seth started out as the school's boiler man living with his wife Meg. He did a lot of poaching but eventually became gamekeeper in 1980. He swapped the Malt Shovel (Beckindale's other pub) for The Woolpack in the summer of 1980. In 1981 he forced local hardnut Tom Merrick out of the village after he tried to frame Jack Sugden in an arson attack. Seth and Meg had marriage difficulties in 1983, which resulted in him having to sleep in a shed at home farm. However he won her back with a bottle of port. Two years latter he opened up a NY social club to create rivalry for The Woolpack however the beer made everyone ill and he only made a profit of 10p before closing down. He later hired entertainment for The Woolpack by getting strippers who could tame snakes to entertain the pub however Amos was having none of it and refused to allow it.
In 1983 it was revealed that Seth was in fact his middle name as his NY Estates work records said A.S. Armstrong. Jackie Merrick asked him what the A stood for and Seth replied "Archibald". He was never known as Archibald and always used his middle name as his common name. Archibald Seth Armstrong was his full name.
In August 1989 a fox was bothering Beckindale; Seth and Jackie went into the woods to shoot it but when Jackie found the fox he accidentally shot himself. Seth was devastated and felt it should have been him who died.
An amusing postscript occurred in 1991, when Alan Turner and Henry Wilks read Amos Brearly's diaries and discovered that Seth was, in fact, an illegal descendant of the Verney family. But any possible claims to ownership of Home Farm had been obscured by NY's purchase and subsequent of the property to Frank Tate. Seth joked that he should to use his officially title Esquire of Beckindale and to use a double-barreled surname Armstrong-Verney. This information was later discovered to have been an April Fool's prank by Seth.
In February 1993 Meg died and Seth's neighbours helped him out with the house work to help him overcome his grief. More trouble arose for him in December when his house was destroyed due to the Emmerdale plane crash. Alan feared Seth had been killed as he had thrown him out of the Woolpack just before the crash happened however he turned up fine. Things looked up for the widower in 1994 when he met old flame from the war, Betty Eagleton, who had also recently being widowed. They planned to marry but eventually just decided to live together and made their relationship official in December 1994 with a 40s-themed night, moving into keepers cottage together a year later. Seth was also claimed a hero that year after accidentally shooting "the beast of Beckindale".
Seth was also good friends with Kim Tate he tried to unsuccessfully defend her in January 1997 when her lover Dave Glover had died and the village had turned on her for her affair with Dave. He later gave her away when she married Steve Marchant in 1998. Seth went to visit his sister in Worthing that year. In October 1998 after The Woolpack was burnt down Seth was chosen to officially reopen it and proudly did and got his own seat at the pub.
In March 2000 Seth was caught up in the bus crash and Betty feared he had been killed. However he was found alive and recovered in hospital. Things got worse for Seth in September when he won money on the horses but was later mugged by some young girls and briefly developed agoraphobia however the villagers helped bring him out of it. Later that year he celebrated his 74th birthday which the village had thought was his 75th and threw him a party in The Woolpack, however he decided not to tell them.
Seth got a computer in 2002 and had a webcam set up for him by Robert Sugden which Seth used to show the village Betty's daily routine in the house getting himself free breakfast's at Cafe Hope in return. When friend Edna Birch told Betty what he was doing she was heartbroken and left Seth telling him via webcam however Seth apologized publicly and they reunited. Seth and Betty were separated again in December 2002 when Betty went to visit Kathy Brookman in Australia who had recently given birth. She returned in March 2003 full of joys of how great Australia was. Seth was worried she may move there but she assured him she'd never leave Emmerdale.
In September 2003 Seth went on an extended holiday to Australia to visit Kathy and never returned to Emmerdale. Betty was upset when he failed to return to the village for Christmas but he made up for it by booking her a flight to come and visit him in Australia. Seth made two final cameo appearances in 2004: the first in the form of a telephone message left on Betty's answering machine and finally on the Internet, as seen on a laptop in The Woolpack that Christmas Eve.
Seth died from a heart attack after having been ill for a while in Australia, whilst on the plane flying back to Britain.
Seth's remains were buried illegally in the woods of Emmerdale, in a storyline that would be briefly revisited in July 2010 after the discovery of an unrelated body in the same woods, Mark Wylde.
Following his break from the role in 2003 and 2004, Richards was keen to reprise his role, but on 11th February 2005 he died of emphysema and several months later, out of respect for the actor, an off-screen death for the character was included in the storyline.