Registrations for the two-day event passed 600 on the opening day, while attendance at the VIP soirée has risen from a mere handfull at the first London Calling to 250 in 2014 - Duplo's 30th anniversary year.
Duplo chairman Robin Greenhalgh paid tribute to two employees who have been with the company from the outset - Kevin Nicholls and Chris Murrell - and urged the company to "keep innovating".
"When we launched the DC-1100 30 years ago it revolutionised the collating of NCR paper. Our opportunity and challenge today is to keep innovating, bringing new products to market that make our customers' businesses more profitable," he said.
Meanwhile, Duplo UK managing director Peter Jolly hailed the success of the six-year-old London Calling, which was born out of a decision to pool the marketing budget for 20 regional events into one pot to fund an "inspirational" annual event at an "iconic venue".
The show has become the highlight of Duplo's sales calendar and Jolly highlighted a raft of first-day deals, including the sale of an £88,000 cutting table to Brilliant Media and debut Lumejet customer Altaimage's acquisition of a Mitamax lay-flat binder.
Other opening day sales included two iSaddle A4 landscape saddle stitchers.
Jolly also paid tribute to the show's 10 partners, including first-time exhibitors Antalis, Lumejet, Neopost, Optimus and Taopix, plus established partners Balreed, Esko, Renz, Vivid and Vpress.
"We bring the partners our customers tell us they want to see," said Jolly.
Meanwhile, Proskills UK managing director Jonathan Ledger officially launched the 2014/15 edition of PrintIT! at London Calling, which will see 10,000 students from more than 400 schools take part in a revamped curriculum with a greater focus on getting apprenticeships and jobs in the industry.
The programme will be supported by a new fundraising programme featuring all of the partners at London Calling 2014, who will each conduct their own month-long fundraising initiative for the charity before passing the baton on to the next partner.
The PassIT! programme, which people will be able to follow via the Twitter hashtag #PassIT!UK, will start with Optimus and be rounded off by Duplo next September.
Additional reporting by Jo Francis
