Loan watch: Britt back among the goals
Southend United ran out 4-1 winners at Plainmoor with Gavin Tomlin also striking twice.
Ryan Jarvis got the Gulls' consolation strike as Assombalonga notched goals number nine and 10 of his 17-match loan spell.
In League One, Portsmouth's Carl Dickinson played his final match for Pompey after returning to Watford yesterday.
The left-back picked up a caution in each of his five games at Fratton Park, ruling him out of Portsmouth's clash against Leyton Orient tonight.
Dickinson lost all five of the matches he played for the south coast outfit.
Joe Garner has enjoyed more success at Carlisle United with six goals in 11 league outings.
The forward drew a blank at the weekend though, as the Cumbrians lost 4-1 at home to Leyton Orient.
Former Watford winger Lee Cook was among the O's scorers.
In League Two, Craig Forsyth & Bradford City were beaten 1-0 at Exeter City, the Scot substituted at half-time.