Follow this link to the NA. This is the hits for Peter Callan in the Medal Indexes.
Note that there was no "Duke of Wellingtons Light Infantry" regiment in the British Army, at least during WWI.
There was a Duke Of Wellington's (West Riding) Regiment.
However, one of the three hits is for a Peter Callan in the Somerset (Prince Albert's) Light Infantry. This may help.
The card should show a MM being awarded if you pay the small fee and down load the cards.
Also surviving service records are extremely scarce from WWI due to German WWII bombing-usually reconded at 10% survival of total and they are called the burnt records. One bright spot is if your relative was invalided out during the war all records to those folks survived and were actually copied by the Mormon's so are available anywhere.
Hope this helps,
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