The hold and win bonus game is the centrepiece of Royal Express. Here is exactly how it triggers and plays out.
Trigger: Land a bonus symbol (golden coin) on reel 1 and reel 3, with a boost symbol appearing on reel 2, all in the same spin. That is three symbols total. Some competing reviews state that six or more bonus symbols are needed. In Royal Express specifically, the confirmed trigger is two bonus symbols plus one boost symbol.
Once activated, the reels clear and only bonus and boost symbols can appear. You start with three respins. Every time a new bonus or boost symbol lands, the respin counter resets to three. Each bonus symbol displays a cash value ranging from 1x to 15x your bet, and special jackpot bonus symbols can also appear, granting a shot at one of the four jackpot tiers.
The round ends when either all nine grid positions are filled or the respin counter reaches zero. At that point every collected value and jackpot prize is summed and paid out.
This mechanic has become a staple across multiple providers precisely because it offers structured anticipation. You watch the grid fill one symbol at a time. Each new landing resets the counter and builds momentum. It is, honestly, the reason most players come back to this slot.
The boost symbol deserves special attention. It is restricted to the middle reel (reel 2). Whenever it lands alongside any bonus symbol, it collects the values of all bonus symbols currently visible on the grid. During the hold and win round, boost symbols remain locked on the middle reel. Each time a new boost lands it re-aggregates all visible bonus values, creating a powerful compounding effect. This is how seemingly modest setups can snowball into substantial payouts.