With the least delay

• Quick as can be
• "Fearless minds climb ___ unto crowns": Shak
• At the earliest opportunity
• Least delayed
• At the earliest date
• "Least said, ___ mended"
• How urgent tasks should be done
• At the first opportunity

Wiktionary Word definitions in Wiktionary
a. (en-superlative of: soon ) adv. 1 (en-superlative of: soon ) 2 (context informal English) very soon.(rfex)