Nigerian international Odion Ighalo scored twice as a buoyant Watford won 3-0 at home to Liverpool to consolidate seventh position in the Premier League, only one point behind the top four.
In the day's other game, West Ham United stayed eighth after a fourth successive draw -- the last three of them goalless -- when they were held by managerless Swansea City, who are still in the bottom three.
The lacklustre defeat by Watford was a bad blow for Juergen Klopp's side, who would have overtaken them with a win but remained ninth, having taken only one point from three games.
Not since April 1987 have Watford, promoted to the top flight this season, won four successive games at this level of English football.
"It was an amazing victory against an amazing team," Quique Sanchez Flores, Watford's manager, told the BBC.
Yet the Spaniard was keen not to get too carried away with his side's progress. "We should be humble, we have a lot of matches to play," he added.
"Four wins back-to-back is massive and starts our so-called tough run that everyone's talking about," jubilant captain Troy Deeney added on Sky Sports.
"We're just doing our stuff and people have got to be worried to come here now."
Deeney and Ighalo have now scored 17 of the team's 21 goals between them this season.
So Watford continue to confound critics who forecast a grim struggle against relegation following a return to the Premier League in May after an eight-year absence.
In 2006/07 they won only five games and finished bottom.
This eighth victory from 17 games leaves them handsomely placed although a tricky programme awaits over the festive period with games against Chelsea, Tottenham Hotspur and Manchester City.
