The charity Help For Heroes has been swamped with donations, leading to its website crashing after Drummer Lee Rigby was murdered while wearing one of its tops.
Help For Heroes offered its thanks for the "extraordinary demonstration of support" which had taken it by surprise.
Posting a statement on its holding page, it said:
Since the sad news emerged that a serving soldier had been murdered in Woolwich, Help for Heroes has been overwhelmed with people spontaneously showing their support for the Armed Forces.
Our website is struggling to cope with this overwhelming reaction from the British public, some of whom are choosing to buy T shirts and hoodies.
This sudden surge of interest in the work we're doing to help the wounded and their families has taken us completely by surprise.
We just want to help, and all funds we receive will be used to provide direct, practical support to those affected by their service to our country.
We ask all our volunteers, fundraisers and donors to remember Lee Rigby's family, colleagues and friends.
Thousands of people have visited our website wishing to donate or to buy H4H T-shirts in an extraordinary demonstration of support and defiance of terrorism.
We are working hard to respond to this level of activity.