The trust's chief grants officer was addressing the Future Trends in Fundraising Question Time, co-ordinated by the Institute of Fundraising.
Speaking to 150 fundraisers from different charities, Thomas said: "We want to move away from the ATM form of fundraising where charities just stick a letter in the post and then wait for the money to come."
Other speakers at the event included Richard Gutch from Futurebuilders, John Kingston from Venturesome and Gerald Oppenheim from the Big Lottery Fund.
Another trend identified by the speakers was the increasing desire of trusts to see the impact of the money they invest. Thomas added: "It's not just a case of spray and pray. We want to know where our money is going."
Kingston agreed. "You need to show that you are having an impact and you need to be clear exactly what it is you want to achieve," he said.
"A good starting point is to make a list of the five things in the world that you want to change as a charity."
Another area that came up in the discussion was the perceived arrogance of charities that believe they should be left to invest their grants without interference. All the speakers agreed this was inappropriate.