Security guards working at Met Police control centres in London struck for 24 hours on Tuesday of this week and on Friday of last week.
The PCS union members walked out at the centres in east and north London where emergency calls are handled.
They are demanding an improved pay offer from outsourcer Engie.
The strike was solid—with 100 percent of union members reportedly out at both sites.
The Met had to use its own police officers to break the strike, taking the places of striking workers.
This means Engie could be fined.
The strikers had support from other PCS branches, including cleaners at HMRC tax offices in Bootle.
The cleaners recently won a victory over pay.
More strikes were set for Friday of this week and Thursday of next week.
Send cheques to the PCS London and south east region, 160 Falcon Road, London SW11 2LN
Messages of support to email@example.com
Attend picket lines on 16 and 22 September