The three tracks ("Iron Maiden", "Invasion" and "Prowler") appear in a rougher form than they would on the band's eponymous debut studio album and subsequent singles, as they were all recorded in one session.

In the midst of punk rock's peak in the UK, Iron Maiden struggled to secure gigs out of the East End of London and decided that a demo would be an ideal way to try to remedy this.

"[3] To save money, the band booked a session New Year's Eve weekend 1978 (30/31 December) which cost them £200,[4] and recorded four songs, "Prowler", "Invasion", "Strange World" and "Iron Maiden".

"[3] Following this New Year's Eve session, the band were due to return a few weeks later to remix and rerecord some parts, however, according to guitarist Dave Murray, "they wanted an extra £50 off us for the master tape and we just didn't have it on us at the time.

"[6] A short time later, Harris and Murray presented a copy of the tape to a DJ named Neal Kay, then running a heavy metal club in Kingsbury, North West London called the Bandwagon Soundhouse.

[9] In late 1979, while waiting to sign their deal with EMI, the band decided to release the demo on their own label, Rock Hard Records, on 9 November 1979.

"[10] Although the original demo had included four songs, "Strange World" was excluded from the record as the band were unsatisfied with the quality of the track's production.

[10] Deciding to release the EP as a memento for fans, the group only printed 5,000 copies, 3,000 of which were sold by mail order in the first week.

[13] The three tracks on it, along with the unreleased recording of "Strange World" from the same sessions, were later reissued on the 4-LP edition of the band's first compilation album, Best of the Beast.

It is equally important for those who play power metal, speed, thrash, death, black, hard rock – almost every genre.